Dissertations / Theses on the topic 'Single-Electron physics'
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1
Granger, Ghislain. "Spin effects in single-electron transistors." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32305.
Abstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2005.Includes bibliographical references (p. 169-175).
Basic electron transport phenomena observed in single-electron transistors (SETs) are introduced, such as Coulomb-blockade diamonds, inelastic cotunneling thresholds, the spin-1/2 Kondo effect, and Fano interference. With a magnetic field parallel to the motion of the electrons, single-particle energy levels undergo Zeeman splitting according to their spin. The g-factor describing this splitting is extracted in the spin-flip inelastic cotunneling regime. The Kondo splitting is linear and slightly greater than the Zeeman splitting. At zero magnetic field, the spin triplet excited state energy and its dependence on gate voltage are measured via sharp Kondo peaks superimposed on inelastic cotunneling thresholds. Singlet-triplet transitions and an avoided crossing are analyzed with a simple two-level model, which provides information about the exchange energy and the orbital mixing. With four electrons on the quantum dot, the spin triplet state has two characteristic energy scales, consistent with a two-stage Kondo effect description. The low energy scale extracted from a nonequilibrium measurement is larger than those extracted in equilibrium.
by Ghislain Granger.
Ph.D.
2
Field, Mark. "Single electron effects in semiconductor microstructures." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308187.
3
Gillingham, David R. "Free electron laser single-particle dynamics theory." Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA246245.
Abstract:
Thesis (M.S. in Physics)--Naval Postgraduate School, December 1990.Thesis Advisor(s): Colson, William B. Second Reader: Maruyama, Xavier K. "December 1990." Description based on title screen as viewed on March 31, 2010. DTIC Identifier(s): Free Electron Lasers, Computerized Simulations, Parmela Computer Programs, Cray Computers, Theses. Author(s) subject terms: Free Electron Lasers, Computerized Simulation. Includes bibliographical references (p. 52-53). Also available in print.
4
Goldhaber-Gordon, David Joshua 1972. "The Kondo effect in a single-electron transistor." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/9450.
Abstract:
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Physics, 1999.Title as it appears in MIT commencement exercises program, June 1999, has the added subtitle: Strong coupling and many body effects.
Includes bibliographical references (p. 115-124).
The Kondo effect, which occurs when a metal with magnetic impurities is cooled to low temperatures, has been a focus of research in solid-state physics for several decades. I have designed, fabricated, and measured a system which behaves as a single "artificial" impurity in a metal, displaying the Kondo effect. This so-called Single-Electron Transistor (SET) has several advantages over the classic bulk Kondo systems. Most obviously, only one impurity is involved, so there is no need to worry about interactions between impurities, or different impurities feeling different environments. But even more importantly all the parameters of the system, such as the binding energy of electrons on the impurity and the tunneling rate between metal and impurity, can be tuned in-situ, allowing detailed quantitative comparison to thirty years of theoretical developments whose details could not be tested in previously-studied Kondo systems.
by David Joshua Goldhaber-Gordon.
Ph.D.
5
Foxman, Ethan Bradley 1966. "Single electron charging and quantum effects in semiconductor nanostructures." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/72770.
6
Dial, Oliver Eugene III. "Single particle spectrum of the two dimensional electron gas." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/45158.
Abstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2007.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 251-265).
Accurate spectroscopy has driven advances in chemistry, materials science, and physics. However, despite their importance in the study of highly correlated systems, two-dimensional systems (2DES) have proven difficult to probe spectroscopically. Typical energy scales are on the order of a millielectron volt (meV), requiring high resolution, while correlated states of interest, such as those found in the integer and fractional quantum Hall effect, are destroyed by excessive electron heating. Approaches based on tunneling have been hampered by problems such as ohmic heating and low in-plane conductivity, while optical approaches probe long-wavelength excitations which can be difficult to interpret. Here we present a refined spectroscopic technique, time domain capacitance spectroscopy (TDCS), with which we measure the single particle density of states (DOS) of a 2DES with temperature-limited resolution. In TDCS, sharp voltage pulses disequilibrate a metallic contact from a nearby 2DES, inducing a tunnel current. We detect this current by monitoring the image charge of the tunneled electrons on a distant electrode. No ohmic contact to the 2DES is required. The technique works when the 2DES is empty or has vanishing in-plane conductivity, as frequently occurs in studying the quantum Hall effect. Using TDCS, we perform unprecedentedly high resolution measurements of the DOS of a cold 2DES in GaAs over a range from 15 meV above to 15 meV below the Fermi surface. We provide the first direct measurements of the width of the single-particle exchange gap and single particle lifetimes in the quantum Hall system. At higher energies, we observe the splitting of highly excited Landau levels by spin polarization at the Fermi surface, demonstrating that the high energy spectrum reflects the low temperature ground state in these highly correlated systems. These measurements bring to light the difficult to reach and beautiful structure present far from the Fermi surface.
by Oliver Eugene Dial, III.
Ph.D.
7
Hemingway, Bryan J. "Magnetoconductance and Dynamic Phenomena in Single-Electron Transistors." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1352397253.
8
Marnham, Lachlan Leslie. "Bi-electron bound states in single- and double-layer graphene nanostructures." Thesis, University of Exeter, 2016. http://hdl.handle.net/10871/23165.
Abstract:
The prototypical exciton model of two interacting Dirac particles in graphene was analysed by Sabio et al, Phys. Rev. B 81, 045428 (2010), and it was found that in one of the electron-hole scattering channels the total kinetic energy vanishes, resulting in a singular behaviour. We show that this singularity can be removed by extending the quasiparticle dispersion, thus breaking the symmetry between upper and lower Dirac cones. The dynamics of an electron-electron pair are then mapped onto that of a single particle with negative mass and anisotropic dispersion. We show that the interplay between dispersion and repulsive interaction can result in the formation of bound, Cooper-pair-like, metastable states in double-layered hybrid structures. We analyse these states by calculating their binding energies, decay rates into the free- electron continuum and semiclassical trajectories. We also analyse the problem of bi-electron pairing with the inclusion of the two dominant many-body effects at zero temperature: screening of the Coulomb interaction by the Dirac sea, and reduction of the available phase space due to Pauli blocking of transitions into the states below the Fermi level. We show that these effects result in strong renormalization of the binding energy, but do not destroy the metastable states. Thus the binding energies are strongly dependent on the chemical potential owing to the combined effects of screening and Pauli blocking. Hence, the quasibound resonances can be tuned by electrostatic doping.
9
Venkatachalam, Vivek. "Single Electron Probes of Fractional Quantum Hall States." Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10478.
Abstract:
When electrons are confined to a two dimensional layer with a perpendicular applied magnetic field, such that the ratio of electrons to flux quanta \((\nu)\) is a small integer or simple rational value, these electrons condense into remarkable new phases of matter that are strikingly different from the metallic electron gas that exists in the absence of a magnetic field. These phases, called integer or fractional quantum Hall (IQH or FQH) states, appear to be conventional insulators in their bulk, but behave as a dissipationless metal along their edge. Furthermore, electrical measurements of such a system are largely insensitive to the detailed geometry of how the system is contacted or even how large the system is... only the order in which contacts are made appears to matter. This insensitivity to local geometry has since appeared in a number of other two and three dimensional systems, earning them the classification of "topological insulators" and prompting an enormous experimental and theoretical effort to understand their properties and perhaps manipulate these properties to create robust quantum information processors. The focus of this thesis will be two experiments designed to elucidate remarkable properties of the metallic edge and insulating bulk of certain FQH systems. To study such systems, we can use mesoscopic devices known as single electron transistors (SETs). These devices operate by watching single electrons hop into and out of a confining box and into a nearby wire (for measurement). If it is initially unfavorable for an electron to leave the box, it can be made favorable by bringing another charge nearby, modifying the energy of the confined electron and pushing it out of the box and into the nearby wire. In this way, the SET can measure nearby charges. Alternatively, we can heat up the nearby wire to make it easier for electrons to enter and leave the box. In this way, the SET is a sensitive thermometer. First, by operating the SET as an electrometer, we measure the local charge of the \(\nu = 5/2\) FQH state. An immediate consequence of measuring fractionally quantized conductance plateaus is that the charge of local excitations should be a fraction of \(e\), the charge of an electron. The simplest charge that would be expected at \(\nu = 5/2\) would \(e/2\). However, if the charged particles that condense into the \(\nu = 5/2\) FQH state are paired, the expected local charge becomes \(e/4\). By watching these local charges being added to compressible puddles at \(\nu = 5/2\) and \(\nu = 5/7\), we find that the local charge at \(\nu = 5/2\) is indeed \(e/4\), indicating that objects of charge \(e\) are pairing to form the ground state of the system. This has implications for the future possibility of detecting non-Abelian braiding statistics in this state, and is described in detail in Chapter 2. By further monitoring how eagerly these \(e/4\) particles enter puddles as we increase the temperature, we can attempt to identify the presence of some excess entropy related to an unconventional degeneracy of their ground state. Such an entropy would be expected if the \(\nu = 5/2\) state exhibited non-Abelian braiding statistics. Progress on these experiments and prospects for building a quantum computer are presented in Chapter 3. Next, by operating the SET as a thermometer, we monitor heat flow along the compressible edge and through the bulk of IQH and FQH states. As an edge is heated and charge on that edge is swept downstream by the external magnetic field, we expect that charge to carry the injected energy in the same downstream direction. However, for certain FQH states, this is not the case. By heating an edge with a quantum point contact (QPC) and monitoring the heat transported upstream and downstream, we find that heat can be transported upstream when the edge contains structure related to \(\nu = 2/3\) FQH physics. Surprisingly, this can be present even when the bulk is in a conventional insulating (IQH) state. Additionally, we unexpectedly find that the \(\nu = 1\) bulk is capable of transporting heat, while the \(\nu = 2\) and \(\nu = 3\) bulk are not. These experiments are presented in Chapter 4. Finally, in Chapter 5, we describe preliminary work on a very different type of topological material, the quantum spin Hall (QSH) insulator. Here, the spin of electrons takes the place of the external magnetic field, creating edge states that propagate in both directions. Each of these edges behaves as an ideal one-dimensional mode, with predicted resistance \(h/e^2\). By creating well-defined regions where these modes can exist, we identify and characterize the conductance associated with topological edges.Physics
10
Erbsen, Wes Corbin. "Non-dissociative single-electron ionization of diatomic molecules." Thesis, Kansas State University, 2013. http://hdl.handle.net/2097/15740.
Abstract:
Master of ScienceDepartment of Physics
Carlos Trallero
Over the past four decades, the single-electron ionization of atoms has been a subject of great interest within the ultra-fast community. While contemporary atomic ionization models tend to agree well with experiment across a wide range of intensities (10[superscript]13-10[superscript]15 W/cm[superscript]2), analogous models for the ionization of molecules are currently lacking in accuracy. The deficiencies present in molecular ionization models constitute a formidable barrier for experimentalists, who wish to model the single-electron ionization dynamics of molecules in intense laser fields. The primary motivation for the work presented in this thesis is to provide a comprehensive data set which can be used to improve existing models for the strong-field ionization of molecules. Our approach is to simultaneously measure the singly-charged ion yield of a diatomic molecule paired with a noble gas atom, both having commensurate ionization potentials. These measurements are taken as a function of the laser intensity, typically spanning two orders of magnitude (10[superscript]13-10[superscript]15 W/cm[superscript]2). By taking the ratio of the molecular to atomic yields as a function of laser intensity, it is possible to "cancel out" systematic errors which are common to both species, e.g. from laser instability, or temperature fluctuations. This technique is very powerful in our ionization studies, as it alludes to the distinct mechanisms leading to the ionization of both molecular and atomic species at the same intensity which are not a function of the experimental conditions. By using the accurate treatments of atomic ionization in tandem with existing molecular ionization models as a benchmark, we can use our experimental ratios to modify existing molecular ionization theories. We hope that the data procured in this thesis will be used in the development of more accurate treatments describing the strong-field ionization of molecules.
11
Rjagopal, Ramasubramaniam. "Correlated single electron transport in capacitively coupled tunnel junction arrays /." view abstract or download file of text, 1999. http://wwwlib.umi.com/cr/uoregon/fullcit?p9957570.
Abstract:
Thesis (Ph. D.)--University of Oregon, 1999.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 95-97). Also available for download via the World Wide Web; free to University of Oregon users. Address:http://wwwlib.umi.com/cr/uoregon/fullcit?p9957570.
12
Abusch-Magder, David 1969. "Artificial atoms and electron puddles : single and double barriers in a silicon MOS system." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10184.
13
Brenner, Rolf Physics Faculty of Science UNSW. "Single-electron transistors for detection of charge motion in the solid state." Awarded by:University of New South Wales. School of Physics, 2004. http://handle.unsw.edu.au/1959.4/20533.
Abstract:
This work investigates advanced single-electron transistor (SET) devices for detection of charge motion in solid-state systems. In particular, novel, nanoscale twin-SET and double-island SET (DISET) detectors are introduced as sensitive charge detectors. Some advantages over conventional SET detectors in terms of noise performance, sensitivity and versatility are pointed out. With the prospect of present, transistor-based microelectronics facing serious limitations due to quantum effects and heat dissipation, alternative computing paradigms ??? such as quantum computers, quantum-dot cellular automata and single-electronics ??? have emerged, promising an extension of highlevel integration and computing power beyond the above limitations. The most promising proposals are based on solid-state systems, and readout of a computational result often requires ultra-sensitive charge detectors capable of sensing the motion of single charges on fast timescales. SETs have been shown to combine all these qualities. However, random fluctuations of the background charge in solid-state systems can affect SETs and cause errors during readout. A twin-SET detector is presented that consists of two independent SETs, which were used to detect controlled single electron transfers on a small, floating metal double-dot. By cross-correlating the two SET signals, rejection of random charge noise is successfully demonstrated, thus decreasing the error probability during readout. Detection of single-electron transfer in a double-dot is also demonstrated using a double-island SET. In addition, conductance suppression in this novel DISET detector allows the detection of electrostatically degenerate charge con- figurations of a double-dot, which cannot be achieved with single-island SETs. We consider the noise performance of the DISET, and an intuitive definition of the DISET charge sensitivity suggests that under certain conditions, DISETs can have a better charge sensitivity than conventional SETs, which would be attractive for quantum limited measurements. Finally we present the first study of a DISET operated at radio-frequencies (rf-DISET), compatible with charge detection on ms timescales. This capability is a prerequisite when reading out the charge state of quantum mechanical systems. A very good charge sensitivity (5.6 x 10i6 e/pHz) and noise temperature (2.1 K) of the rf-DISET setup are reported.
14
Wang, Zhendong. "Photophysics of Single-walled Carbon Nanotubes and Thin-film Conjugated Polymers Within π-electron Model." Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/195107.
Abstract:
Electron-electron interaction effects play important role in the photophysics of complex organic materials such as π-conjugated polymers and single-walled carbon nanotubes. Our theoretical work within a π-electron model captures the essential mechanism of the photophysics in these apparently different π-conjugated systems. In both polymer and nanotube systems, we not only explain existing experiments but also make testable predictions. In the area of π-conjugated polymers, we develop a theory of the electronic structure and photophysics of interacting chains to understand the differences between solutions and films. While photoexcitation generates only the optical exciton in solutions, the optical exciton as well as weakly allowed excimers are generated in films. Photoinduced absorption in films is primarily from the lowest excimer. We are also able to explain peculiarities associated with photoluminescence, including delayed photoluminescence and its quenching by electric field. We thereby resolve controversies in the field that are more than a decade old. In the area of single-walled carbon nanotubes, we have investigated the exciton theory of the electronic structure of both semiconducting and metallic nanotubes. We are able to determine quantitatively the exciton energies and exciton binding energies of the nanotubes, in both longitudinal and transverse directions. Our estimate of longitudinal exciton energies and exciton binding energies of semiconducting tubes are the best quantitative fits to the experimental results to date. We also make predictions that the longitudinal exciton binding energies of metallic tubes are comparable to those of semiconducting tubes, in contradiction to recently published results. Our work demonstrates a universality in the photophysics of S-SWCNTs and PCPs that arises from their common quasi-one-dimensionality and π-conjugation.
15
Mannix, Daniel. "X-ray and neutron scattering studies of f-electron multilayers and single crystals." Thesis, University of Liverpool, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263708.
16
Randeria, Mallika. "On the design of single electron transistors for the measurement of spins in phosphorus doped silicon." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/78520.
Abstract:
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 66-67).
Phosphorus doped silicon is a prime candidate for spin based qubits. We plan to investigate a novel hybrid technique that combines the advantages of spin selective optical excitations with that of electrical readout measurements to detect spin defects in semiconductors. In this thesis, I present my work on the design and fabrication of single electron transistors (SETs) for the electrical readout of the spin state of phosphorus doped silicon. For such highly sensitive measurements, it is necessary for the characteristic energy of the SET to be larger than thermal fluctuations. My goal was to design and fabricate SETs on P doped Si that function at temperatures of about 2K. This necessitated minimizing the tunnel junction area through optimized lithography and evaporation procedures. I have produced SETs with charging energies of - 0.85 meV corresponding to a temperature of ~ 10 K. These SETs have a charge sensitivity of ~ 2 x 10 -⁴ e/[square root]Hz at 10 mK but have yet to be tested at temperatures of 2K. The mechanism of detection involves exciting the P donor to a P+ ion that then shifts the electrochemical potential near the SET, creating a sharp peak in the current through the SET. This can ultimately be used for single shot readout and thus for a measurement of the spin state of the electron - a promising system for quantum computation, magnetometry and spintronics.
by Mallika Randeria.
S.B.
17
Smith, Neil Ronald. "USING ELECTRON BEAM LITHOGRAPHY TO MAKE ELECTRODES FOR SINGLE MOLECULE ELECTRONICTS." Miami University / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=miami1123213432.
18
Anaya, Armando Alonso. "Spin Valve Effect in Ferromagnet-Superconductor-Ferromagnet Single Electron Transistor." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6864.
Abstract:
This thesis describes a research of suppression of superconducting gap in a superconducting island of a Ferromagnetic-Superconducting-Ferromagnetic Single-Electron-Transistor due to the fringing magnetic fields produced by the ferromagnetic leads. The devices are working below the critical temperature of the superconducting gap. A model is proposed to explain how the fringing magnetic field produced by the leads is strong enough to suppress the superconducting gap. The peak of the fringing magnetic field produced by one lead reaches 5000 oe. It is observed an inverse tunneling magneto resistance during the suppression of the superconducting gap, obtaining a maximum absolute value 500 times greater than the TMR in the normal state where the efficiency of the spin injection is low.
It is concluded that the suppression of the superconducting gap is due to fringing magnetic field and not to the spin accumulation because the low efficiency of the spin injection. It is suggested a new geometry to reduce the effect of the fringing magnetic field so it can be obtained a suppression of the superconductivity due to the spin accumulation. It is described the qualitatively behavior of the IV characteristic when the suppression of the superconductivity is due to spin accumulation.
19
Ferguson, R. Matthew. "Steps toward the creation of a carbon nanotube single electron transistor." Pomona College, 2003. http://ccdl.libraries.claremont.edu/u?/stc,0.
Abstract:
This report details work toward the fabrication of a single-electron transistor created from a single-walled carbon nanotube (SWNT). Specifically discussed is a method for growing carbon nanotubes (CNTs) via carbon vapor deposition (CVD). The growth is catalyzed by a solution of 0.02g Fe(NO3)3·9H2O, 0.005g MoO2(acac)2, and 0.015g of alumina particles in 15mL methanol. SWNT diameter ranges from 0.6 to 3.0 nm. Also discussed is a method to control nanotube growth location by patterning samples with small islands of catalyst. A novel “maskless” photolithographic process is used to focus light from a lightweight commercial digital projector through a microscope. Catalyst islands created by this method are approximately 400 μm2 in area.
20
Karlsson, Susanne. "Single and Accumulative Electron Transfer – Prerequisites for Artificial Photosynthesis." Doctoral thesis, Uppsala universitet, Kemisk fysik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-122206.
Abstract:
Photoinduced electron transfer is involved in a number of photochemical and photobiological processes. One example of this is photosynthesis, where the absorption of sunlight leads to the formation of charge-separated states by electron transfer. The redox equivalents built up by successive photoabsorption and electron transfer is further used for the oxidation of water and reduction of carbon dioxide to sugars. The work presented in this thesis is part of an interdisciplinary effort aiming at a functional mimic of photosynthesis. The goal of this project is to utilize sunlight to produce renewable fuels from sun and water. Specifically, this thesis concerns photoinduced electron transfer in donor(D)-photosensitizer(P)-acceptor(A) systems, in mimic of the primary events of photosynthesis. The absorption of a photon typically leads to transfer of a single electron, i.e., charge separation to produce a single electron-hole pair. This fundamental process was studied in several molecular systems. The purpose of these studies was optimization of single electron transfer as to obtain charge separation in high yields, with minimum losses to competing photoreactions such as energy transfer.Also, the lifetime of the charge separated state and the confinement of the electron and hole in three-dimensional space are important in practical applications. This led us to explore molecular motifs for linear arrays based on Ru(II)bis-tridentate and Ru(II)tris-bidentate complexes. The target multi-electron catalytic reactions of water-splitting and fuel production require a build-up of redox equivalents upon successive photoexcitation and electron transfer events. The possibilities and challenges associated with such processes in molecular systems were investigated. One of the studied systems was shown to accumulate two electrons and two holes upon two successive excitations, without sacrificial redox agents and with minimum yield losses. From these studies, we have gained better understanding of the obstacles associated with step-wise photoaccumulation of charge and how to overcome them.
21
Dhital, Bharat. "Single-molecule interfacial electron transfer dynamics in solar energy conversion." Bowling Green State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1477997482545831.
22
Deshpande, Veeresh. "Scaling Beyond Moore: Single Electron Transistor and Single Atom Transistor Integration on CMOS." Phd thesis, Université de Grenoble, 2012. http://tel.archives-ouvertes.fr/tel-00813508.
Abstract:
La r eduction (\scaling") continue des dimensions des transistors MOS- FET nous a conduits a l' ere de la nano electronique. Le transistor a ef- fet de champ multi-grilles (MultiGate FET, MuGFET) avec l'architecture \nano l canal" est consid er e comme un candidat possible pour le scaling des MOSFET jusqu' a la n de la roadmap. Parall element au scaling des CMOS classiques ou scaling suivant la loi de Moore, de nombreuses propo- sitions de nouveaux dispositifs, exploitant des ph enom enes nanom etriques, ont et e faites. Ainsi, le transistor mono electronique (SET), utilisant le ph enom ene de \blocage de Coulomb", et le transistor a atome unique (SAT), en tant que transistors de dimensions ultimes, sont les premiers disposi- tifs nano electroniques visant de nouvelles applications comme la logique a valeurs multiples ou l'informatique quantique. Bien que le SET a et e ini- tialement propos e comme un substitut au CMOS (\Au-del a du dispositif CMOS"), il est maintenant largement consid er e comme un compl ement a la technologie CMOS permettant de nouveaux circuits fonctionnels. Toutefois, la faible temp erature de fonctionnement et la fabrication incompatible avec le proc ed e CMOS ont et e des contraintes majeures pour l'int egration SET avec la technologie FET industrielle. Cette th ese r epond a ce probl eme en combinant les technologies CMOS de dimensions r eduites, SET et SAT par le biais d'un sch ema d'int egration unique a n de fabriquer des transistors \Trigate" nano l. Dans ce travail, pour la premi ere fois, un SET fonction- nant a temp erature ambiante et fabriqu es a partir de technologies CMOS SOI a l' etat de l'art (incluant high-k/grille m etallique) est d emontr e. Le fonctionnement a temp erature ambiante du SET n ecessite une le (ou canal) de dimensions inf erieures a 5 nm. Ce r esultat est obtenu grce a la r eduction du canal nano l "trigate" a environ 5 nm de largeur. Une etude plus ap- profondie des m ecanismes de transport mis en jeu dans le dispositif est r ealis ee au moyen de mesures cryog eniques de conductance. Des simula- tions NEGF tridimensionnelles sont egalement utilis ees pour optimiser la conception du SET. De plus, la coint egration sur la m^eme puce de MOS- FET FDSOI et SET est r ealis ee. Des circuits hybrides SET-FET fonction- nant a temp erature ambiante et permettant l'ampli cation du courant SET jusque dans la gamme des milliamp eres (appel e \dispositif SETMOS" dans la litt erature) sont d emontr es de m^eme que de la r esistance di erentielle n egative (NDR) et de la logique a valeurs multiples. Parall element, sur la m^eme technologie, un transistor a atome unique fonc- tionnant a temp erature cryog enique est egalement d emontr e. Ceci est obtenu par la r eduction de la longueur de canal MOSFET a environ 10 nm, si bien qu'il ne comporte plus qu'un seul atome de dopant dans le canal (dif- fus ee a partir de la source ou de drain). A basse temp erature, le trans- port d' electrons a travers l' etat d' energie de ce dopant unique est etudi e. Ces dispositifs fonctionnent egalement comme MOSFET a temp erature am- biante. Par cons equent, une nouvelle m ethode d'analyse est d evelopp ee en corr elation avec des caract eristiques a 300K et des mesures cryog eniques pour comprendre l'impact du dopant unique sur les caracteristiques du MOSFET a temp erature ambiante.
23
Dorr, Joshua Charles. "Quantum Jump Spectroscopy of a Single Electron in a New and Improved Apparatus." Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:11187.
Abstract:
The 2008 measurement of the electron magnetic moment is the most precisely measured property of an elementary particle, with an astonishing precision of 0.28 parts per trillion. It makes possible the most precise determination of the fine structure constant and the most precise test of quantum electrodynamics and the Standard Model of particle physics. This thesis describes the installation of a new apparatus designed to have improved stability, more optimal control over the radiation field and inhibited spontaneous emission, and narrower resonance lines.Physics
24
Bartlett, Kurtis David. "First Measurements of the Parity-Violating and Beam-Normal Single-Spin Asymmetries in Elastic Electron-Aluminum Scattering." W&M ScholarWorks, 2018. https://scholarworks.wm.edu/etd/1550153799.
Abstract:
The Qweak collaboration has made the first measurements of the elastic parity-violating and beam-normal single-spin asymmetries from the 27Al nucleus. Both are the result of ancillary measurements conducted during the Qweak experiment at Jefferson Lab. The goal of the experimental was to determine the proton's weak charge, Qp W, via a measurement of the elastic parity-violating electron-proton scattering asymmetry. During the experiment, ancillary measurements were made with different beam configurations on a separate aluminum alloy target, in an effort to directly measure the aluminum background coming from the experiment's liquid hydrogen target cell.
This dissertation discusses three primary results: the parity-violating 27Al asymmetry analysis used to correct for the aluminum target background in the final Qweak analysis, its extended analysis leading to the extraction of the pure elastic parity-violating 27Al asymmetry, and the determination of the elastic beam-normal single-spin 27Al asymmetry. The parity-violating result was also used to make a semi model-independent determination 27Al neutron distribution radius, an important test for models used to describe neutron-rich matter. The beam-normal single-spin asymmetry stands to possibly shed light on an observed disagreement between theory and a previous measurement performed on 208Pb, as 27Al is the next highest atomic mass nucleus to have this observable measured.
The elastic parity-violating 27Al asymmetry was found to be $1.927 ± 0.173 ppm at ⟨ Q2 ⟩ = 0.0236 ± 0.0001 GeV2. This measured parity-violating asymmetry implies a 27Al neutron distribution radius of $3.024 ± 0.104 fm. Calculating the difference between this radius and the 27 Al proton distribution radius yields the neutron skin, which was found to be $0.092 ± 0.104 fm. This skin value is consistent with zero, within its uncertainty, and it confirms the naive expectation for a light nucleus like 27Al.
The beam-normal single-spin 27Al asymmetry was found to be $-16.322 ± 2.679 ppm at ⟨ Q ⟩ = 0.154 GeV. This value agrees with the previous observed trend of beam-normal single-spin asymmetries measured from light nuclei, which motivates the need for future measurements of higher atomic mass nuclei.
25
Tekiel, Antoni. "Ultra-high vacuum fabrication of nanoscale systems for studying single-electron charging by room-temperature atomic force microscopy." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=119570.
Abstract:
In this work we describe ultra-high vacuum fabrication of a nanoscale system that reveals Coulomb blockade at room temperature and its characterization by single-electron sensitive electrostatic force microscopy (e-EFM). The system consists of Au nanoparticles separated from an Fe(001) back electrode by a crystalline ultra-thin NaCl film. Due to the small size of the nanoparticles (3.5 nm high), the Coulomb blockade can be observed at room temperature. An atomic force microscopy (AFM) cantilever is used as a movable gate to charge individual nanoparticles via single-electron tunneling from the back electrode. At the same time the tunneling is detected by measuring frequency shift and damping of the oscillating cantilever. The e-EFM technique can overcome limitations of other characterization methods based on lithographic fabrication. So far, however, it has been successfully used only at low-temperatures. In this work, we extend the e-EFM technique to room temperature by carefully tuning the sample design and fabrication relative to the cantilever response to achieve maximum sensitivity. To grow atomically defined tunnel barriers we investigate the morphology of MgO and NaCl ultra-thin films on Fe(001) surfaces by non-contact-AFM and low energy electron diffraction (LEED). First, we demonstrate that the quality of MgO films, typically grown in ultra-high vacuum (UHV) by electron-beam evaporation, can be improved by using reactive deposition method that gives full control over the gaseous species existing in the evaporated beam. Second, we investigate the effects of temperature and oxygen presence on the growth of NaCl on Fe(001). As a result, we develop a protocol to grow NaCl films on the Fe(001)-p(1x1)O surface in a layer-by-layer mode, yielding atomically flat films with 40-60 nm wide terraces (on a 12 ML thick film) and with far fewer defects than the MgO films. Using the NaCl film as a tunnel barrier that can be easily adjusted by modifying the film thickness we characterize single-electron charging at room temperature of individual Au nanoparticles formed after thermal evaporation onto a 6 monolayer thick NaCl film. We demonstrate how a combination of e-EFM and finite element electrostatic simulation can be used for revealing electronic and morphological properties of individual Au nanoparticles. As a result, the electron addition energy, the capacitance, tunneling rates and an approximated shape of an individual nanoparticle have been determined. Numerical simulations point towards a total capacitance dominated by the mutual capacitance between the nanoparticle and the back electrode. A comparison with the experimental value, determined from measurement of the addition energy, indicates that the nanoparticles should be modeled as truncated spheres in order to reduce the mutual capacitance to the substrate. This observation has a fundamental impact on the design of nanoelectronic circuits, where the components have to meet desired requirements for capacitances that determine coupling and charging effects. The fabrication flexibility and the fact that all measurements were performed in-situ on samples prepared under ultra-clean conditions make the presented system attractive for further studies. In particular, this approach can be used to study quantum mechanically coupled quantum dots and the catalytic activity of Au nanoclusters at room temperature.Dans ce travail, nous décrivons la fabrication sous ultra haut vide (UHV) d'un système à l'échelle nanométrique qui révèle le blocage de Coulomb à température de la pièce, ainsi que sa caractérisation par microscopie à force électrostatique sensible à un électron (single-electron sensitive electrostatic force microscopy, e-EFM). Le système est constitué de nanoparticules d'or séparées d'une électrode de Fe(001) par un film cristallin ultra mince de NaCl. Dû à la petite taille des nanoparticules (3.5 nm maximum), le blocage de Coulomb est observable à température ambiante. Un cantilever de microscope à force atomique (MFA) est utilisé comme une grille électrique déplaçable pour charger individuellement les nanoparticules par le passage de charge élémentaire par effet tunnel à partir de l'électrode. Ce passage d'électron est détecté en mesurant simultanément le changement de fréquence de résonance, ainsi que l'amortissement de l'oscillation du cantilever. La technique e-EFM permet de contourner certaines limitations inhérentes aux techniques de caractérisation basées sur la fabrication par lithographie. Toutefois, cette technique a été appliquée avec succès seulement à basses températures. Dans ce travail, nous étendons la technique e-EFM à température ambiante par un ajustement minutieux du design de l'échantillon et de sa fabrication en fonction de la réponse du cantilever de sorte à maximiser la sensibilité de la mesure. Pour croître une jonction tunnel définie à l'échelle atomique, nous étudions la morphologie de couches minces de MgO et de NaCl sur une surface de Fe(001) par microscopie à force atomique non-contact et par diffraction d'électrons lents (Low Energy Electrons Diffraction, LEED). Premièrement, nous démontrons que la qualité des couches minces de MgO, typiquement crûes sous UHV par évaporation sous faisceau d'électrons (electron-beam evaporation), peut être améliorée par l'utilisation d'une méthode de déposition réactive qui donne un contrôle total sur les espèces gazeuses présentes dans le faisceau d'évaporation. Deuxièmement, nous étudions l'effet de la température et de la présence d'oxygène sur la croissance du NaCl sur une surface de Fe(001). Conséquemment, un protocole pour la croissance de films de NaCl sur une surface de Fe(001)-p(1x1)O déposés couche par couche. Ces films plats à l'échelle atomique présentent des terrasses de 40-60 nm de large et contiennent beaucoup moins de défauts cristallins que les films de MgO.En utilisant ces couches minces de NaCl comme jonction tunnel facilement ajustables par une modification de leur épaisseur, nous caractérisons le chargement d'électron à température ambiante de nanoparticules individuelles formées par évaporation thermique sur un film de 6 monocouches de NaCl. Nous montrons comment la combinaison de la technique e-EFM et de simulations électrostatiques par éléments finis peut être utilisée pour révéler les propriétés électroniques et morphologiques de nanoparticules d'or individuelles. Ainsi, l'énergie de chargement, la capacitance, la fréquence de passage par effet tunnel et la forme approximative des nanoparticules ont été déterminées. Des simulations numériques montrent que la capacitance totale est dominée par la capacitance mutuelle entre la nanoparticule et l'électrode. En comparant avec les valeurs expérimentales, déterminées par une mesure de l'énergie de chargement, on montre que les nanoparticules devraient être modélisées par des sphères tronquées pour réduire la capacitance mutuelle avec le substrat. Cette observation a un impact fondamental pour le design de circuits nanoélectroniques dans lesquels les composantes doivent avoir des capacitances définies, étant donné que celles-ci déterminent les effets de couplage et de chargement.La flexibilité de la technique de fabrication et le fait que toutes les mesures ont été effectuées in situ sur des échantillons dans des conditions ultra propres rendent le système attrayant pour de futures études.
26
Lasorak, Pierre. "A search for neutrino-induced single photons and measurement of oscillation analysis systematic errors with electron and anti-electron neutrino selections, using the off-axis near detector of the Tokai to Kamioka experiment." Thesis, Queen Mary, University of London, 2018. http://qmro.qmul.ac.uk/xmlui/handle/123456789/39755.
Abstract:
This thesis describes the search for neutrino-production of single photons using the off-axis near detector at 280 metres (ND280) of the T2K experiment. A photon selection is used to perform the searches using the first Fine Grained Detector (FGD1) of the ND280. The thesis also highlights the importance of systematic uncertainties in the analysis, since the selection is background dominated. After careful characterisation of the systematic uncertainties and estimation of the efficiency, it is concluded that, with the selected 39 data events and the expected background of 45 events, the limit for neutrino-induced single photons, at T2K energies, is 0:0903 x 10-38cm2/nucleon. This result can be compared with the expected limit of 0:1068 x 10-38cm2/nucleon. Using ND280's neutrino energy distribution (peaked at 600 MeV), NEUT predicts a flux-averaged cross section of 0:000239 x 10-38cm2/nucleon. A fit to the muon and electron (anti-) neutrinos selections in the ND280 was performed. The aim of this analysis is to use a data-driven method to constrain the electron (anti-) neutrinos background events at SK, the far detector and electron neutrino cross section parameters for oscillation analyses. These are fundamental inputs in the context of the searches for Charge-Parity (CP) violation in the neutrino sector. After a fit to the nominal Monte Carlo was realised, the electron neutrino and anti-neutrino cross section normalisation uncertainties are found to be 7.6% and 19.3%, repectively. Although these numbers are much higher than the assumed 3% uncertainty of all the CP violation searches performed at T2K up to now, the difference in the δCP log-likelihood is found to be acceptable as the one sigma contours are not very different and the exclusion of the δCP = 0 is roughly the same.
27
Teeling-Smith, Richelle Marie. "Single Molecule Electron Paramagnetic Resonance and Other Sensing and Imaging Applications with Nitrogen-Vacancy Nanodiamond." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1424779811.
28
Wang, He. "From few-cycle femtosecond pulse to single attosecond pulse-controlling and tracking electron dynamics with attosecond precision." Diss., Kansas State University, 2010. http://hdl.handle.net/2097/4393.
Abstract:
Doctor of PhilosophyDepartment of Physics
Zenghu Chang
The few-cycle femtosecond laser pulse has proved itself to be a powerful tool for controlling the electron dynamics inside atoms and molecules. By applying such few-cycle pulses as a driving field, single isolated attosecond pulses can be produced through the high-order harmonic generation process, which provide a novel tool for capturing the real time electron motion. The first part of the thesis is devoted to the state of the art few-cycle near infrared (NIR) laser pulse development, which includes absolute phase control (carrier-envelope phase stabilization), amplitude control (power stabilization), and relative phase control (pulse compression and shaping). Then the double optical gating (DOG) method for generating single attosecond pulses and the attosecond streaking experiment for characterizing such pulses are presented. Various experimental limitations in the attosecond streaking measurement are illustrated through simulation. Finally by using the single attosecond pulses generated by DOG, an attosecond transient absorption experiment is performed to study the autoionization process of argon. When the delay between a few-cycle NIR pulse and a single attosecond XUV pulse is scanned, the Fano resonance shapes of the argon autoionizing states are modified by the NIR pulse, which shows the direct observation and control of electron-electron correlation in the temporal domain.
29
Rajagopal, Senthil Arun. "SINGLE MOLECULE ELECTRONICS AND NANOFABRICATION OF MOLECULAR ELECTRONIC DEVICES." Miami University / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=miami1155330219.
30
Pica, Giuseppe. "Donor electron states for silicon quantum computing : from single spins to scaled architectures." Thesis, University of St Andrews, 2015. http://hdl.handle.net/10023/7816.
Abstract:
This PhD work took place in the framework of theoretical research aimed at implementation of quantum computing schemes and algorithms in solid state devices. The electron and nuclear spins of dopant atoms implanted in silicon crystals, that already lie at the core of commercial diodes and the photovoltaic industry, are able to store quantum information longer than anything else in the solid state. Controlled manipulations of silicon qubits depend on the ability to tune the nanoscopic donor electron state: we provide a complete theoretical picture that includes, within the insightful and analytic framework of effective mass theory, the effects of the non-trivial silicon conduction band and the different lattice distortions caused by the implantation of the donor species. Calibration of the multi-valley bulk theory to account for binding energies and electron-nuclear hyperfine couplings allows improved estimates of the exchange splittings between two neighbouring donors, that provide the simplest handle for tuning two-qubit operations. Further refinements to our approach lead to exceptional agreement with experimental measurements of Stark effects, where an external electric field is used to enable local single qubit manipulations within global driving fields: we set reliable thresholds on such gating speeds across all group V donors. Finally, we propose a scalable scheme for silicon quantum computing that relies on the coherent transfer of information from Si:Bi donors, that are established as excellent memory qubits, to surface quantum dots that are easier to manipulate, within a topological surface code which enables outstanding tolerance to errors. Analysis of the optimal working regimes and inclusion of the leading sources of decoherence allow us to set out a robust design of the basic building block of future realizations.
31
Barlow, M. J. "Cold and hot electron magnetotransport in In0̲.̲5̲3̲Ga0̲.̲4̲7̲As-InP single heterostructures and quantum wells." Thesis, University of Essex, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383357.
32
Walker, Mark Allen. "Single-Electron Structure and Dynamics in the Strong-Field Photoionization of Noble Gas Atoms and Diatomic Molecules." The Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu1039125206.
33
Hermelin, Sylvain. "Transport d'un électron unique dans des nanostructures." Phd thesis, Université de Grenoble, 2012. http://tel.archives-ouvertes.fr/tel-00721761.
Abstract:
Un effort mondial existe actuellement dans le but de réaliser un ordinateur quantique. Un tel dispositif permettrait d'implémenter des algorithmes plus rapides que les algorithmes classiques pour certaines tâches (recherche dans des bases de données, factorisation d'entiers). Il permettrait également de simuler des systèmes quantiques de manière beaucoup plus efficace qu'un ordinateur classique. L'obtention de ce gain en puissance nécessite d'intriquer un grand nombre de bits quantiques (qubits). Celle ci suppose de pouvoir déplacer un qubit d'un point à un autre de l'espace. Dans cette thèse, nous démontrons une première étape vers le déplacement d'un qubit de spin électronique : un électron unique est déplacé, à la demande, entre deux boîtes quantiques distantes de quelques microns. Le transport est réalisé à l'aide d'une onde acoustique de surface qui entraîne l'électron. Le transfert a été réalisé avec une efficacité de 90 % et déclenché à la nanoseconde. Ces résultats ouvrent la voie à la réalisation d'expériences d'optique quantique électronique avec une détection évènement par évènement. L'envoi d'un électron sur deux initialement présents ouvre la voie à la génération de paires d'électrons distants et intriqués.
34
Waidyawansa, D. Buddhini P. "A 3% Measurement of the Beam Normal Single Spin Asymmetry in Forward Angle Elastic Electron-Proton Scattering using the Qweak Setup." Ohio University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1375705139.
35
Liu, Tai-Min. "Electronic Interactions in Semiconductor Quantum Dots and Quantum Point Contacts." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1311773375.
36
Cunningham, Eric Flint. "Photoemission by Large Electron Wave Packets Emitted Out the Side of a Relativistic Laser Focus." BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/3054.
Abstract:
There are at least two common models for calculating the photoemission of accelerated electrons. The 'extended-charge-distribution' method uses the quantum probability current (multiplied by the electron charge) as a source current for Maxwell's equations. The 'point-like-emitter' method treats the electron like a point particle instead of like a diffuse body of charge. Our goal is to differentiate between these two viewpoints empirically. To do this, we consider a large electron wave packet in a high-intensity laser field, in which case the two viewpoints predict measurable photoemission rates that differ by orders of magnitude. Under the treatment of the 'extended-charge-distribution' model, the strength of the radiated field is significantly limited by interferences between different portions of the oscillating charge density. Alternatively, no suppression of photoemission occurs under the 'point-like-emitter' model because the electron is depicted as having no spatial extent. We designed an experiment to characterize the photoemission rates of electrons accelerated in a relativistic laser focus. Free electron wave packets are produced through ionization by an intense laser pulse at the center of a large vacuum chamber. These quantum wave packets can become comparable in size to the laser wavelength through natural spreading and interactions with the sharp ponderomotive gradients of the laser focus. Electron radiation emitted out the side of the focus is collected by one-to-one imaging into a 105-micron gold-jacketed fiber, which carries the light to a single photon detector located outside the chamber. The electron radiation is red-shifted due to mild relativistic acceleration, and we use this signature to spectrally filter the outgoing light to discriminate against background. In addition, the temporal resolution of the electronics allows distinction between light that travels directly from the focus into the collection system and laser light that may scatter from the chamber wall.
37
Pothier, H. "BLOCAGE DE COULOMB ET TRANSFERT D'ELECTRONS UN PAR UN." Phd thesis, Université Pierre et Marie Curie - Paris VI, 1991. http://tel.archives-ouvertes.fr/tel-00185219.
Abstract:
Les fluctuations de point zéro de la charge sur la capacité d'une jonction tunnel connectée à un circuit de polarisation sont, dans quasiment toutes les situations expérimentales, supérieures à la charge de l'électron. De ce fait, les effets de la granularité de l'électricité sont masqués, sauf dans les circuits qui contiennent une «île», électrode connectée au reste du circuit seulement par des jonctions tunnel et des capacités. La charge de l'île étant quantifiée, ses fluctuations sont bloquées. Si la capacité de l'île est suffisamment petite et la température suffisamment basse, aucun électron ne peut pénétrer sur l'île par effet tunnel à cause de l'accroissement d'énergie électrostatique que cela entraînerait. Nous avons observé cet effet, appelé «blocage de Coulomb», dans la «boîte à électrons», où une île est délimitée par une jonction tunnel et une capacité. Une source de tension couplée à l'île à travers la capacité permet d'y contrôler le nombre d'électrons. Nous avons conçu et fait fonctionner deux dispositifs à jonctions tunnel nanométriques basés sur ce principe, le «tourniquet» et la «pompe», à travers lesquels le courant est contrôlé électron par électron. Dans nos expériences, la précision du transfert est de l'ordre du pourcent. Elle devrait être un million de fois plus grande dans des versions de ces dispositifs comportant plus de jonctions. On pourrait alors les utiliser pour une nouvelle mesure de la constante de structure fine alpha.
38
Geffroy, Clément. "Impulsions ultra-courte d'électron unique pour les qubits volants." Electronic Thesis or Diss., Université Grenoble Alpes, 2023. http://www.theses.fr/2023GRALY101.
Abstract:
La seconde révolution quantique du XXe siècle a contribué à un essor technologique en physique du solide. Les techniques d'ingénierie des matériaux couplées à celles de nanofabrication moderne ont favorisé le perfectionnement de sources d'électrons uniques sur demande. De par leur incroyable précision, elles sont désormais utilisées en métrologie et leur potentiel s'étend au récent domaine de l'optique quantique électronique, notamment à un candidat prometteur pour l’information quantique : le qubit volant électronique. Ces bits quantiques sont créés par de courtes impulsions de tension et la manipulation de leur état quantique se fait à la volée. À ce jour, l’impulsion de tension la plus courte atteint 27 ps, sur puce, dans un environnement cryogénique. Cependant, en raison de l'atténuation et de la dispersion du signal dans les lignes coaxiales, l'accès à des régimes quantiques électroniques d’échelle temporelle plus rapide demeure hors de portée.En revanche, grâce à l'avènement des lasers à impulsions ultracourtes et aux progrès en photonique et plasmonique, la technologie des photocommutateurs peut permettre la génération d'impulsions électromagnétiques de l'ordre de la picoseconde. La large bande passante de ces technologies opto-électroniques THz pourrait venir à bout de la barrière technique à laquelle sont confrontés les équipements électroniques standards. Bien que largement développées dans le cadre d'applications à température ambiante, les démonstrations d'intégration de ces technologies à une architecture quantique en environnement cryogénique restent toujours peu nombreuses. La réalisation d'une telle expérience débloquerait de nouvelles voies de recherche pour l'étude des dynamiques des dispositifs quantiques électroniques en physique du solide.Dans ce manuscrit, nous présentons la mise au point d'une installation expérimentale pouvant générer des impulsions de tension picoseconde en environnement cryogénique pour des applications de qubits volants. Un laser femtoseconde génère des impulsions qui sont injectées dans des fibres optiques intégrées à basse température. Fabriqué à la surface de GaAs basse température (LT-GaAs), un photocommutateur est cointégré au circuit quantique formé à partir d'un gaz d'électrons bidimensionnels (2DEG) à haute mobilité. Du fait de la réponse opto-électronique extrêmement rapide du LT-GaAs, le photocommutateur convertit les impulsions optiques en impulsions de tension d'une durée de quelques picosecondes seulement. Grâce à des guides d'ondes coplanaires (CPW) THz, l'impulsion est acheminée vers le 2DEG, où elle est utilisée comme source d'électrons uniques ultracourts.Pour effectuer la mesure pompe-sonde et résoudre le profil dynamique de telles impulsions, une installation expérimentale originale, impliquant des positionneurs piézo-électriques et des protocoles d'alignement à basses températures, a été mise en place. Comme preuve de concept, nous rapportons d'abord la caractérisation à 300 K d'impulsions électroniques d'une durée de 1.9 ps. Dans un deuxième temps, nous refroidissons le système à 4K, élargissant la preuve de concept aux environnements cryogéniques par la mesure d'impulsions de 2.3 ps. Ensuite, en intégrant une structure 2DEG au circuit THz, des excitations de plasmons THz ont pu être observées dans une cavité Fabry-Pérot. La fréquence de leur mode fondamental a été comparée à un modèle analytique, révélant des informations sur la densité de porteur du gaz électronique sous illumination. Parallèlement, des développements importants ont été menés sur la conception des CPWs dans le but de minimiser les réflexions indésirables du signal ainsi que les pertes par dispersion. Ces travaux ouvriront la voie à l'intégration d'impulsions de tension picoseconde dans les dispositifs quantiques nanoélectroniques et le contrôle de qubits volants électroniques par des grilles électrostatiques THz ultrarapidesThe second quantum revolution of the 20th century contributed to a technological expansion in solid-state physics. Modern nanofabrication coupled to material processing techniques have facilitated the development of on-demand single-electron sources. With their remarkable precision, they are currently used for metrology purposes and hold key potential for the recent field of research of electron quantum optics, including a promising candidate for quantum information: the electron flying qubit. These quantum bits are created by short voltage pulses and manipulation of their quantum state occurs on-the-fly. The shortest voltage pulse reported so far attains 27 ps, on-chip, in a cryogenic environment. However, suffering from attenuation and dispersion in coaxial lines, accessibility to electronic quantum regimes at faster time scale remains out-of-reach.On the contrary, empowered by the advent of ultrafast lasers and progress in photonics and plasmonics, photo-conductive-switch technology can allow the generation of electromagnetic pulses with picosecond duration. The large bandwidth of these THz opto-electronic technologies could overcome the technical bottleneck faced by standard electronic equipment. While they have been widely developed for room temperature applications, demonstrations of their integration along-side a quantum architecture in a cryogenic environment are still limited. The realisation of such an experiment would unlock new research directions for studying the dynamics of solid-state electronic quantum devices.In this manuscript, we present the development of an experimental setup to generate picosecond voltage pulses in a cryogenic environment for flying qubit applications. A femtosecond laser generates pulses that are injected into optical fibres and integrated at low temperatures. Fabricated on the surface of Low Temperature grown GaAs (LT-GaAs), a photoconductive-switch is co-integrated to the quantum circuit formed on a high mobility two-Dimensional Electron Gas (2DEG). Owing to the extremely fast opto-electronic response of the LT-GaAs, the photo-conductive device converts optical pulses into voltage pulses with a duration as short as a few picoseconds. Using a THz CoPlanar Waveguide (CPW) circuit, the pulse is conveyed toward the 2DEG, where it is used as an ultra-short single-electron source.To perform pump-probe measurement and resolve the dynamic profile of such pulses, an original experimental setup, involving piezo-electric positioners and alignment protocols at low-temperatures, was implemented. As proof of concept, we first report the characterisation at 300 K of electronic pulses with 1.9 ps duration. In a second step, we cool down the system to 4 K and measure 2.3 ps wide pulses, thus expanding the proof of concept to cryogenic environments. Then, by integrating a 2DEG structure along-side the THz circuit, we were able to excite THz plasmons in a Fabry-Pérot cavity. The characteristic frequency of their fundamental mode was compared to an analytical model that revealed information about the carrier density of the electron gas under illumination. In parallel, extensive developments were carried out on the design of CPWs in order to minimise undesirable signal reflections as well as dispersion losses. Finally, with the prospect of measuring and controlling the propagation of picosecond electron pulse in quantum channels directly with ultrafast THz electrostatic gates, the fabrication of the next generation of devices was initiated. This work will pave the way for on-chip integration of picosecond voltage pulses into quantum nanoelectronics devices and ultrafast control of electronic flying qubits
39
Freulon, Vincent. "Étude de la décohérence de paquets d'onde monoélectroniques dans les canaux de bord de l'effet Hall quantique entier." Thesis, Paris, Ecole normale supérieure, 2014. http://www.theses.fr/2014ENSU0023/document.
Abstract:
Cette thèse est consacrée à l'étude de la décohérence de paquets d'onde mono-électroniques injectés dans un conducteur quantique balistique. Les paquets d'onde sont générés à l'aide d'une capacité mésoscopique, utilisée comme source d'électrons uniques, qui sont émis à la demande dans le canal de bord externe de l'effet Hall quantique entier. Deux telles sources indépendantes et synchronisées sont positionnées sur les bras d'entrée d'une lame séparatrice électronique. La mesure des fluctuations (bruit) du courant dans les bras de sortie permet de caractériser les interférences à deux électrons se produisant sur la lame séparatrice. De cette manière, on réalise l'analogue électronique de l'interféromètre de Hong-Ou-Mandel (HOM). Il apparaît que le contraste de la figure d'interférence dépend de la forme des paquets d'onde injectés. Cette perte de cohérence est imputée au couplage capacitif, dû à l'interaction coulombienne, entre le canal de bord externe et les autres canaux de bord co-propageants, qui constituent un environnement contrôlé pour le canal externe. Afin de valider cette hypothèse, une seconde expérience est réalisée. La capacité mésoscopique y est utilisée dans un autre régime de fonctionnement, dans lequel elle permet de générer une excitation collective de la densité de charge du canal externe, appelée magnéto-plasmon de bord. En caractérisant la propagation du magneto-plasmon de bord en fonction de la fréquence d'excitation, on peut sonder l'interaction Coulombienne entre deux canaux de bord. Ces mesures montrent que cette interaction est responsable de l'apparition de deux modes propres de la propagation : un mode "chargé" rapide et un mode "neutre" lent. Elles permettent de caractériser quantitativement la vitesse de propagation du mode neutre. Les résultats de cette seconde expérience sont ensuite utilisés pour établir que la perte de contraste, observée dans l'expérience HOM, est essentiellement due à l'interaction entre canaux de bord. Ce couplage est responsable de la destruction des quasi-particules injectées par la source, un électron se séparant (ou fonctionnalisant) en deux pulses de charge e/2 au fil de sa propagation. Durant le processus de fractionnalisation, l'état généré dans le canal de bord externe s'intrique avec son environnement (canaux de bord co-propageants) entraînant la réduction du contraste dans l'expérience HOM. Ces observations ouvrent la voie à de nouvelles expériences plus complexes telles que la tomographie de l'état du paquet d'onde sur la lame séparatrice (pour valider complètement le scénario de destruction des quasi-particules) ou la protection de la cohérence de l'état dans le canal de bord externeThis manuscript is devoted to the study of the decoherence of single electronic wavepackets injected in a balistic quantum conductor. The single electrons are emitted on-demand using a mesoscopic capacitor in the outer edge channel of the integer quantum Hall effect. Two independent and synchronized sources are located on the input arms of an electronic beam-splitter. The measurement of the current fluctuations (noise) in the output arms allows for the characterization of two-electron interferences occuring on the beam-splitter. This realizes the electronic analog of the Hong-Ou-Mandel (HOM) interferometer. It appears that the contrast of the interference pattern depends on the shape of the emitted wavepackets. This loss of electronic coherence is caused by the capacitive coupling, due to the Coulomb interaction, between the outer edge channel and the other channels, which constitute a controlled environment for the outer channel. In order to validate this scenario, a second experiment has been realized. The mesoscopic capacitor is used in a different regime, in which it generates a collective charge density wave called edge magnetoplasmon. By characterizing the propagation of the edge magnetoplasmon as a function of frequency, one can probe the Coulomb interaction between the channels. The measurements show that this interaction is responsible for the appearance of two propagating eigenmodes: a fast charge mode and a slow neutral mode, and provide the determination of the slow mode velocity. The results of this second experiment are then used to establish that the reduction of the contrast observed in the HOM experiment is caused by this interchannel interaction. It is responsible for the destruction of the quasiparticles emitted by the source which fractionalize in charge pulses of charge e/2 along propagation. During the fractionalization process, the state generated in the outer channel gets entangled with the environment (other channels), hence reducing the contrast in the HOM experiment. More complex experiments, such as the tomography of the emitted electornic wavepacket to validate the full decoherence scenario, or the implementation of decoherence protection schemes can be envisioned in the future
40
Lahme, Stefan. "Femtosecond single-electron diffraction." Diss., Ludwig-Maximilians-Universität München, 2014. http://nbn-resolving.de/urn:nbn:de:bvb:19-178346.
Abstract:
Die grundlegenden Funktionsprinzipien der Natur zu verstehen, ist seit jeher Antrieb der Naturwissenschaften. Verhalten und Eigenschaften von Festkörpern werden dabei häufig von dynamischen Prozessen auf atomarer Skala (< 10^-10 m) bestimmt, welche typischerweise auf Zeitskalen im Bereich von zehn Femtosekunden (10^-15 s) bis hin zu vielen Picosekunden (10^-12 s) ablaufen. Zeitaufgelöste Elektronenbeugung an kristallinen Festkörpern ermöglicht die direkte Beobachtung solcher Prozesse in Raum und Zeit. Die bislang mit diesem Verfahren erreichte Zeitauflösung von etwa 100 fs eignet sich jedoch nicht zur Beobachtung der schnellsten Prozesse in Festkörpern. Auch die, zur zuverlässigen Auflösung von großen Elementarzellen molekularer Kristalle erforderliche, transversale Kohärenz ist unzureichend. Eine wesentliche Ursache für diese beiden Probleme liegt in der gegenseitigen Coulomb-Abstoßung der Elektronen innerhalb eines Pulses und den daraus resultierenden Veränderungen der Geschwindigkeitsverteilungen in radialer und longitudinaler Richtung. Während erstere zu verringerter transversaler Kohärenz führt, hat letztere längere Elektronenpulsdauern und damit eine begrenzte Zeitauflösung zur Folge.
In dieser Arbeit wird ein Messaufbau zur zeitaufgelösten Elektronenbeugung vorgestellt, welcher auf der Erzeugung von nur einem Elektron pro Puls basiert. Aufgrund der Vermeidung von Coulomb-Abstoßung innerhalb der Pulse ist dieser Ansatz eine vielversprechende Basis zur konzeptionell nahezu unbegrenzten Verbesserung der Zeitauflösung. Eine hier eigens entwickelte, thermisch stabilisierte Elektronenquelle garantiert einen hohen Grad an Kohärenz bei gleichzeitig hervorragender Langzeitstabilität der Photoelektronenausbeute. Insbesondere letzteres ist für zeitaufgelöste Beugungsexperimente mit Einzeleelektronen aufgrund der längeren Integrationszeit unerlässlich, konnte jedoch durch vorhergehende Quellen nicht erreicht werden. Darüber hinaus werden in dieser Arbeit die besonderen Ansprüche der Einzelelektronenbeugung an die zu untersuchenden Materialien diskutiert und Strategien zur Vermeidung von Schäden an der Probe durch akkumulierte Anregungsenergie entwickelt. Diese erfordern neue Schwerpunkte bei der Probenpräparation, welche entwickelt und diskutiert werden. Die Beobachtung der komplexen Relaxationsdynamik in Graphit-Dünnfilmen mit zeitaufgelöster Einzelelektronenbeugung demonstriert abschließend die generelle Eignung dieses Verfahrens als zuverlässige Methodik zur Untersuchung von reversibler, struktureller Dynamik in Festkörpern mit atomarer Auflösung.
Nicht-relativistische Einzelelektronenpulse können mit Hilfe von zeitabhängigen Feldern bei Mikrowellenfrequenzen bis in den 10 fs-Bereich komprimiert werden, eventuell sogar
bis in den Attosekundenbereich. Die hier demonstrierte langzeitstabile und hochkohärente Elektronenquelle, sowie die Methodiken zur Probenpräparation und zeitaufgelösten Beugung
mit Einzelelektronenpulsen liefern die Basis für zukünftige Experimente dieser Art.The understanding of nature’s fundamental processes has always been the goal of science. Often, the behavior and properties of condensed matter are determined by dynamic pro- cesses on the atomic scale (< 10^-10 m). The relevant time scales for these processes range from tens of femtoseconds (10^−15 s) to several picoseconds (10^−12 s). Time-resolved electron diffraction on crystalline solids allows the direct observation of such processes in space and time. However, the state-of-the-art temporal resolution is insufficient to observe the fastest processes in solids. The transverse coherence is insufficient to resolve large unit cells of molecular crystals. One major origin for both of these problems is that the electron within the pulse repel each other, resulting in a change of the radial and longitudinal velocity distribution. The former leads to a decrease transverse coherence while the former leads to a significant increase in electron pulse duration, limiting temporal resolution. In this work, a setup for time-resolved electron diffraction is introduced that works with electron pulses each containing only a single electron. Circumventing Coulomb repulsion, this approach can lead to in principle nearly unlimited, improvement of temporal resolu- tion. The novel, thermally stabilized single-electron gun developed here provides a high degree of transverse coherence and excellent long-term stability of the photoemission yield at the same time. The latter is crucial for time-resolved diffraction experiments due to the long integration times required when working with single-electron pulses and has not been achieved prior to this work. Furthermore, the special requirements of single-electron diffraction on the materials under study are discussed. Strategies for avoidance of sam- ple damage from accumulated excitation energy are developed, requiring new emphases in sample preparation. The observation of the complex relaxation dynamics of graphite thin films using time-resolved single-electron diffraction finally demonstrates the general feasi- bility of this technique as a reliable methodology for investigation of reversible, structural dynamics in solids with atomic resolution. Using time-dependent fields at microwave frequencies, non-relativistic single-electron pulses can be compressed to 10 fs and possibly even down to the attosecond regime. The long-term stable and high-coherence electron gun demonstrated here as well as the method- ology developed for sample preparation and time-resolved electron diffraction using single- electron pulses provide the basis for such experiments in the future.
41
Deshpande, Veeresh. "Intégration de transistor mono-électronique et transistor à atome unique sur CMOS." Phd thesis, Université de Grenoble, 2012. http://tel.archives-ouvertes.fr/tel-00844406.
Abstract:
La réduction (" scaling ") continue des dimensions des transistors MOSFET nous a conduits à l'ère de la nanoélectronique. Le transistor à effet de champ multi-grilles (MultiGate FET, MuGFET) avec l'architecture "nanofil canal" est considéré comme un candidat possible pour le scaling des MOSFET jusqu'à la fin de la roadmap. Parallèlement au scaling des CMOS classiques ou scaling suivant la loi de Moore, de nombreuses propositions de nouveaux dispositifs, exploitant des phénomènes nanométriques, ont été faites. Ainsi, le transistor monoélectronique (SET), utilisant le phénomène de "blocage de Coulomb", et le transistor à atome unique (SAT), en tant que transistors de dimensions ultimes, sont les premiers dispositifs nanoélectroniques visant de nouvelles applications comme la logique à valeurs multiples ou l'informatique quantique. Bien que le SET a été initialement proposé comme un substitut au CMOS ("Au-delà du dispositif CMOS"), il est maintenant largement considéré comme un complément à la technologie CMOS permettant de nouveaux circuits fonctionnels. Toutefois, la faible température de fonctionnement et la fabrication incompatible avec le procédé CMOS ont été des contraintes majeures pour l'intégration SET avec la technologie FET industrielle. Cette thèse répond à ce problème en combinant les technologies CMOS de dimensions réduites, SET et SAT par le biais d'un schéma d'intégration unique afin de fabriquer des transistors " Trigate " nanofil. Dans ce travail, pour la première fois, un SET fonctionnant à température ambiante et fabriqués à partir de technologies CMOS SOI à l'état de l'art (incluant high-k/grille métallique) est démontré. Le fonctionnement à température ambiante du SET nécessite une île (ou canal) de dimensions inférieures à 5 nm. Ce résultat est obtenu grâce à la réduction du canal nanofil ''trigate'' à environ 5 nm de largeur. Une étude plus approfondie des mécanismes de transport mis en jeu dans le dispositif est réalisée au moyen de mesures cryogéniques de conductance. Des simulations NEGF tridimensionnelles sont également utilisées pour optimiser la conception du SET. De plus, la cointégration sur la même puce de MOSFET FDSOI et SET est réalisée. Des circuits hybrides SET-FET fonctionnant à température ambiante et permettant l'amplification du courant SET jusque dans la gamme des milliampères (appelé "dispositif SETMOS" dans la littérature) sont démontrés de même que de la résistance différentielle négative (NDR) et de la logique à valeurs multiples. Parallèlement, sur la même technologie, un transistor à atome unique fonctionnant à température cryogénique est également démontré. Ceci est obtenu par la réduction de la longueur de canal MOSFET à environ 10 nm, si bien qu'il ne comporte plus qu'un seul atome de dopant dans le canal (diffusée à partir de la source ou de drain). A basse température, le transport d'électrons à travers l'état d'énergie de ce dopant unique est étudié. Ces dispositifs fonctionnent également comme MOSFET à température ambiante. Par conséquent, une nouvelle méthode d'analyse est développée en corrélation avec des caractéristiques à 300K et des mesures cryogéniques pour comprendre l'impact du dopant unique sur l'échelle MOSFET à température ambiante.
42
Fricke, Lukas [Verfasser]. "A self-referenced single-electron current source / Lukas Fricke." Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover (TIB), 2015. http://d-nb.info/1069937371/34.
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Lahme, Stefan Verfasser], and Ferenc [Akademischer Betreuer] [Krausz. "Femtosecond single-electron diffraction / Stefan Lahme. Betreuer: Ferenc Krausz." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2014. http://d-nb.info/1065611218/34.
44
Henkel, Florian. "Photoionisation detection of single 87Rb-atoms using channel electron multipliers." Diss., lmu, 2011. http://nbn-resolving.de/urn:nbn:de:bvb:19-136329.
45
Balewski, Jonathan B. [Verfasser]. "A single electron in a Bose-Einstein condensate / Jonathan B. Balewski." München : Verlag Dr. Hut, 2014. http://d-nb.info/1050331826/34.
46
Kirchner, Friedrich. "Ultrashort and coherent single-electron pulses for diffraction at ultimate resolutions." Diss., Ludwig-Maximilians-Universität München, 2013. http://nbn-resolving.de/urn:nbn:de:bvb:19-170030.
47
Hong, Sungkun. "Nanoscale Magnetic Imaging with a Single Nitrogen-Vacancy Center in Diamond." Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10671.
Abstract:
Magnetic imaging has been playing central roles not only in fundamental sciences but also in engineering and industry. Their numerous applications can be found in various areas, ranging from chemical analysis and biomedical imaging to magnetic data storage technology. An outstanding problem is to develope new magnetic imaging techniques with improved spatial resolutions down to nanoscale, while maintaining their magnetic sensitivities. For instance, if detecting individual electron or nuclear spins with nanomter spatial resolution is possible, it would allow for direct imaging of chemical structures of complex molecules, which then could bring termendous impacts on biological sciences. While realization of such nanoscale magnetic imaging still remains challenging, nitrogen-vacancy (NV) defects in diamond have recently considered as promising magnetic field sensors, as their electron spins show exceptionally long coherence even at room temperature. This thesis presents experimental progress in realizing a nanoscale magnetic imaging apparatus with a single nitrogen-vacancy (NV) color center diamond. We first fabricated diamond nanopillar devices hosting single NV centers at their ends, and incorporated them to a custom-built atomic force microscope (AFM). Our devices showed unprecedented combination of magnetic field sensitivity and spatial resolution for scanning NV systems. We then used these devices to magnetically image a single isolated electronic spin with nanometer resolution, for the first time under ambient condition. We also extended our study to improve and generalize the application of the scanning NV magnetometer we developed. We first introduced magnetic field gradients from a strongly magnetized tip, and demonstrated that the spatial resolution can be further improved by spectrally distinguishing identical spins at different locations. In addition, we developed a method to synchronize the periodic motion of an AFM tip and pulsed microwave sequences controlling an NV spin. This scheme enabled employment of 'AC magnetic field sensing scheme' in imaging samples with static and spatially varying magnetizations.Engineering and Applied Sciences
48
Oron-Carl, Matti [Verfasser]. "Electron phonon coupling in single walled carbon nanotubes / Matti Oron-Carl." Karlsruhe : Forschungszentrum Karlsruhe, 2006. http://d-nb.info/983081085/34.
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Sethubalasubramanian, Nandhavel [Verfasser]. "Counting statistics of electron transfer in a single quantum dot / Nandhavel Sethubalasubramanian." Hannover : Technische Informationsbibliothek (TIB), 2017. http://d-nb.info/1137061367/34.
50
Gliserin, Alexander. "Towards attosecond 4D imaging of atomic-scale dynamics by single-electron diffraction." Diss., Ludwig-Maximilians-Universität München, 2014. http://nbn-resolving.de/urn:nbn:de:bvb:19-181849.
Abstract:
Many physical and chemical processes which define our daily life take place on atomic scales in space and time. Time-resolved electron diffraction is an excellent tool for investigation of atomic-scale structural dynamics (4D imaging) due to the short de Broglie wavelength of fast electrons. This requires electron pulses with durations on the order of femtoseconds or below. Challenges arise from Coulomb repulsion and dispersion of non-relativistic electron wave packets in vacuum, which currently limits the temporal resolution of diffraction experiments to some hundreds of femtoseconds.
In order to eventually advance the temporal resolution of electron diffraction into the few-femtosecond range or below, four new concepts are investigated and combined in this work: First, Coulomb repulsion is avoided by using only a single electron per pulse, which does not repel itself but interferes with itself when being diffracted from atoms. Secondly, dispersion control for electron pulses is implemented with time-dependent electric fields at microwave frequencies, compressing the duration of single-electron pulses at the expense of simultaneous energy broadening. Thirdly, a microwave signal used for electron pulse compression is derived from an ultrashort laser pulse train. Optical enhancement allows a temporal synchronization between the microwave field and the laser pulses with a precision below one femtosecond. Fourthly, a cross-correlation between laser and electron pulses is measured in this work with the purpose of determining the possible temporal resolution of diffraction experiments employing compressed single-electron pulses. This novel characterization method uses the principles of a streak camera with optical fields and potentially offers attosecond temporal resolution.
These four concepts show a clear path towards improving the temporal resolution of electron diffraction into the few-femtosecond domain or below, which opens the possibility of observing electron densities in motion. In this work, a compressed electron pulse's duration of 28±5 fs full width at half maximum (12±2 fs standard deviation) at a de Broglie wavelength of 0.08 Å is achieved. Currently, this constitutes the shortest electron pulses suitable for diffraction, about sixfold shorter than in previous work. Ultrafast electron diffraction now meets the requirements for investigating the fastest primary processes in molecules and solids with atomic resolution in space and time.