Journal articles: 'Electron phase coherence length'

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Pouydebasque, A., A. G. Pogosov, M. V. Budantsev, D. K. Maude, A. E. Plotnikov, A. I. Toropov, and J. C. Portal. "Electron phase coherence length in a lattice of antidots." Physica B: Condensed Matter 298, no. 1-4 (April 2001): 287–90. http://dx.doi.org/10.1016/s0921-4526(01)00320-9.

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Putzke, Carsten, Maja D. Bachmann, Philippa McGuinness, Elina Zhakina, Veronika Sunko, Marcin Konczykowski, Takashi Oka, et al. "h/e oscillations in interlayer transport of delafossites." Science 368, no. 6496 (June 11, 2020): 1234–38. http://dx.doi.org/10.1126/science.aay8413.

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Microstructures can be carefully designed to reveal the quantum phase of the wave-like nature of electrons in a metal. Here, we report phase-coherent oscillations of out-of-plane magnetoresistance in the layered delafossites PdCoO2 and PtCoO2. The oscillation period is equivalent to that determined by the magnetic flux quantum, h/e, threading an area defined by the atomic interlayer separation and the sample width, where h is Planck’s constant and e is the charge of an electron. The phase of the electron wave function appears robust over length scales exceeding 10 micrometers and persisting up to temperatures of T > 50 kelvin. We show that the experimental signal stems from a periodic field modulation of the out-of-plane hopping. These results demonstrate extraordinary single-particle quantum coherence lengths in delafossites.

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ALMASAN, C. C., G. A. LEVIN, E. CIMPOIASU, T. STEIN, C. L. ZHANG, M. C. DEANDRADE, M. B. MAPLE, HONG ZHENG, A. P. PAULIKAS, and B. W. VEAL. "Relationship between Conductivity and Phase Coherence Length in Cuprates." International Journal of Modern Physics B 13, no. 29n31 (December 20, 1999): 3618–22. http://dx.doi.org/10.1142/s0217979299003556.

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The large (102–105) and strongly temperature dependent resistive anisotropy η=(σab/σc)1/2 of cuprates perhaps holds the key to understanding their normal state in-plane σab and out-of-plane σc conductivities. It can be shown that η is determined by the ratio of the phase coherence lenghts ℓi in the respective directions: [Formula: see text]. In layered crystals in which the out-of-plane transport is incoherent, ℓc is fixed, equal to the interlayer spacing. As a result, the T-dependence of η is determined by that of ℓab, and vice versa, the in-plane phase coherence lenght can be obtained directly by measuring the resistive anisotropy. We present data for hole-doped YBa2Cu3Oy (6.3<y<6.9) and Y1-xPrxBa2O7-δ(0<x≤0.55) and show that σcb of crystals with different doping levels can be well described by a two parameter universal function of the in-plane phase coherence length. In the electron-doped Nd2-xCexCuO4-y, the dependence σab(η) indicates a crossover from incoherent transport in the c-direction.

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TRALLE, IGOR, and WIOLETTA PAŚKO. "SPIN BALLISTIC TRANSPORT AND SPIN CURRENT OSCILLATIONS IN MESOSCOPIC LOOP STRUCTURES." International Journal of Modern Physics B 21, no. 08n09 (April 10, 2007): 1674–80. http://dx.doi.org/10.1142/s0217979207043415.

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In the paper a theory of quantum interference in a loop structure caused by spin coherent transport and the Larmor precession of the electron spin is presented. The 'spin ballistic' regime is supposed to occur when the phase relaxation length of the spin part of electron wave function is much greater than the phase relaxation length of the 'orbital' part. If magnetic fields in two arms of the structure are different, the spin part of the wave function acquires a phase shift due to spin precession around the field. If the structure length L is chosen to be [Formula: see text], It is possible to 'wash out' the quantum interference related to the phase coherence of the 'orbital part' of the wave function, retaining at the same time that related to the phase coherence of the spin part and to reveal the corresponding conductance oscillations. Different mechanisms of spin relaxation as well as their influence on the spin transport are considered. The quantum interference in the time-dependent magnetic field is also discussed and similarities between this effect and Josephson one, as well as their differences are considered.

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Hirai, Hiroshi, Susumu Komiyama, Kazuo Nakamura, and Fumiyuki Nihey. "Phase-coherence length in a two-dimensional electron gas at high magnetic fields." Physica B: Condensed Matter 184, no. 1-4 (February 1993): 34–37. http://dx.doi.org/10.1016/0921-4526(93)90317-y.

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SUGAHARA, MASANORI, and NIKOLAI N. BOGOLUBOV. "THEORY OF NO-FIELD QUANTUM HALL EFFECT BASED ON PHASE-CHARGE BOSON WAVE FUNCTION." Modern Physics Letters B 16, no. 28n29 (December 20, 2002): 1083–95. http://dx.doi.org/10.1142/s0217984902004615.

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The derivation of the non-magnetic Laughlin state and other macroscopic quantum states in the semi-localized 2D electron system in the network of circular molecular orbits is made by the study of zero-point plasma oscillation. In the imaginary time representation, the electric field is transformed to the vector potential. After the cancellation of the mean-field component of the inter-electron repulsive field with the ion-lattice field, the boson Hamiltonian with respect to the phase-charge fluctuation is obtained using a Chern–Simons gauge field. Based on the resultant boson wave function, the macroscopic quantum state in hole doping is found to lead to a superfluidity that is described by a coherent function when λΘ > λQ, and to the particle-number-definite state described by a Laughlin function when λQ > λΘ, where λΘ is the phase-coherence length and λQ is the incompressibility length.

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Levin, G. A., E. Cimpoiasu, H. Zheng, A. P. Paulikas, B. W. Veal, Shi Li, M. B. Maple, and C. C. Almasan. "Conductivity and phase coherence length of single electrons in layered cuprates." Europhysics Letters (EPL) 57, no. 1 (January 2002): 86–92. http://dx.doi.org/10.1209/epl/i2002-00545-8.

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Kramer, B., and J. Mašek. "Influence of the phase coherence length on ballistic transport." Zeitschrift für Physik B Condensed Matter 76, no. 4 (December 1989): 457–62. http://dx.doi.org/10.1007/bf01307895.

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SUGAHARA, MASANORI, and NIKOLAI N. BOGOLUBOV. "FIELD-THEORETIC FOUNDATION OF NO-FIELD QUANTUM HALL EFFECT." Modern Physics Letters B 16, no. 18 (August 10, 2002): 645–59. http://dx.doi.org/10.1142/s0217984902004196.

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Recently, the authors discussed the possibility of the macroscopic quantum state similar to the Quantum Hall Effect in a semi-localized 2D electron system with a toroidal electron-wave amplitude in the absence of any magnetic field. In order to give the concrete statistical foundation of the study, the fermion-boson statistical transformation of the 2D electron system is made using a Chern–Simons gauge potential. Based on the solution of the resultant boson-type Hamiltonian, we construct the fermion-type solution via a unitary transformation. It is shown that the solution in the form of Laughlin function is stable when electrons form pairs. In the presence of hole doping, the pair Laughlin function leads to a representation of a superconducting state when the phase-coherence length λΘ exceeds the incompressibility length λQ, but when λΘ< λQ, it leads to a macroscopic quantum state characterized by particle-number definiteness.

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Hirai, Hiroshi, Susumu Komiyama, Kazuo Nakamura, and Fumiyuki Nihey. "Proposed measurements of the phase‐coherence length in a two‐dimensional electron gas at high magnetic fields." Journal of Applied Physics 71, no. 9 (May 1992): 4390–98. http://dx.doi.org/10.1063/1.350777.

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Fournier, P., C. J. Lobb, and R. L. Greene. "Saturation of the phase coherence length at low temperatures in Pr1.95Ce0.05CuO4." Physica C: Superconductivity 341-348 (November 2000): 1941–42. http://dx.doi.org/10.1016/s0921-4534(00)01413-1.

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Goldman, M. V., M. M. Oppenheim, and D. L. Newman. "Theory of localized bipolar wave-structures and nonthermal particle distributions in the auroral ionosphere." Nonlinear Processes in Geophysics 6, no. 3/4 (December 31, 1999): 221–28. http://dx.doi.org/10.5194/npg-6-221-1999.

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Abstract. Bipolar wave structures and nonthermal particle distributions measured by the FAST satellite in regions of downward current are interpreted in terms of the nonlinear evolution of a two-stream instability. The instability results in holes, both in the electron distribution in phase space and in the electron density in real space. The wave potential energy, which traps the electrons, has a single minimum, and the associated electric field is bipolar. The early bipolar structures are coherent over hundreds of Debye lengths in the direction perpendicular to the magnetic field. After thousands of plasma periods the perpendicular coherence is lost, the structures break up, and electrostatic whistlers begin to dominate. Simulations and preliminary analysis of this breakup and emission process are presented.

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Schafer, Lothar, Yury I. Tarasov, Aleksandr V. Koshelev, and Anatoly A. Ischenko. "ULTRAFAST ELECTRON CRYSTALLOGRAPHY AND NANOCRYSTALLOGRAPHY: FOR CHEMISTRY, BIOLOGY AND MATERIALS SCIENCE. PART I. ULTRAFAST ELECTRON CRYSTALLOGRAPHY." IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENIY KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA 60, no. 5 (June 23, 2017): 4. http://dx.doi.org/10.6060/tcct.2017605.5608.

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The direct probing and understanding of the dynamics of chemical and biological processes occurring in condensed matter, is currently in its early stages. Progress in this field has been pushed by the development of methods for the study of the structural dynamics of matter in a state far from equilibrium, including extreme states. The forthcoming information serves as the basis for testing new theoretical approaches to the description of the substance in casually connected triad "structure-dynamics-function". Observation of the dynamic behavior of matter in the space-time continuum on ultrashort time scales is a necessary first step in the explanation and, ultimately, control of far from equilibrium processes, and functionality of the systems studied. The method of ultrafast electron crystallography (UEC) makes it possible to investigate transient nonequilibrium structures, which yield decisive information about the structural dynamics of the phase transitions and coherent dynamics of the nuclei in the solid state, on the surface, and in macromolecular systems. In recent years, the electron bunch path length in the UEC apparatus diminished significantly, while the accelerating voltage increased considerably. Therefore, femtosecond electron pulses were obtained. A technique of radio frequency grouping of electrons was proposed to increase the electron pulse brightness. The method of electron field emission was used to increase the spatial coherence, and ponderomotive wave front acceleration was applied to reduce the mismatch between the velocities of the light and electron pulses and to contract the electron bunches. These achievements have opened up new possibilities for studying the coherent structural dynamics – atomic and molecular movie with femtosecond temporal resolution. The results of several internationally renowned research groups are included and cited.

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Hiramoto, Toshiro, Kazuhiko Hirakawa, Yasuhiro Iye, and Toshiaki Ikoma. "Phase coherence length of electron waves in narrow AlGaAs/GaAs quantum wires fabricated by focused ion beam implantation." Applied Physics Letters 54, no. 21 (May 22, 1989): 2103–5. http://dx.doi.org/10.1063/1.101177.

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Hasselbach, F., and A. Schäfer. "Interferometric (Fourier-Spectroscopic) Measurement of Electron Energy Distributions." Proceedings, annual meeting, Electron Microscopy Society of America 48, no. 2 (August 12, 1990): 110–11. http://dx.doi.org/10.1017/s0424820100134144.

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Möllenstedt and Wohland proposed in 1980 two methods for measuring the coherence lengths of electron wave packets interferometrically by observing interference fringe contrast in dependence on the longitudinal shift of the wave packets. In both cases an electron beam is split by an electron optical biprism into two coherent wave packets, and subsequently both packets travel part of their way to the interference plane in regions of different electric potential, either in a Faraday cage (Fig. 1a) or in a Wien filter (crossed electric and magnetic fields, Fig. 1b). In the Faraday cage the phase and group velocity of the upper beam (Fig.1a) is retarded or accelerated according to the cage potential. In the Wien filter the group velocity of both beams varies with its excitation while the phase velocity remains unchanged. The phase of the electron wave is not affected at all in the compensated state of the Wien filter since the electron optical index of refraction in this state equals 1 inside and outside of the Wien filter.

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16

Katsuyama, T., and K. Ogawa. "Extended phase coherence length of excitonic polaritons in a quantum well waveguide." Semiconductor Science and Technology 5, no. 5 (May 1, 1990): 446–48. http://dx.doi.org/10.1088/0268-1242/5/5/013.

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Rezikyan, Aram, James A. Belcourt, and Michael M. J. Treacy. "Interferometric Diffraction from Amorphous Double Films." Microscopy and Microanalysis 21, no. 5 (October 2015): 1348–60. http://dx.doi.org/10.1017/s1431927615014981.

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AbstractWe explore the interference fringes that arise in diffraction patterns from double-layer amorphous samples where there is a substantial separation, up to about a micron, between two overlapping thin films. This interferometric diffraction geometry, where both waves have interacted with the specimen, reveals phase gradients within microdiffraction patterns. The rapid fading of the observed fringes as the magnitude of the diffraction vector increases confirms that displacement decoherence is strong in high-energy electron scattering from amorphous samples. The fading of fringes with increasing layer separation indicates an effective illumination coherence length of about 225 nm, which is consistent with the value of 270 nm expected for the heated Schottky field emitter source. A small reduction in measured coherence length is expected because of the additional energy spread induced in the beam after it passes through the first layer.

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CZART, WOJCIECH R., and STANISŁAW ROBASZKIEWICZ. "SUPERCONDUCTIVITY OF SYSTEMS WITH COEXISTING ITINERANT ELECTRONS AND LOCAL PAIRS." International Journal of Modern Physics B 15, no. 23 (September 20, 2001): 3125–42. http://dx.doi.org/10.1142/s021797920100718x.

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Phase diagrams and electromagnetic properties of the system of coexisting itinerant (c)-electrons and localized (d)-electrons which can form real space local pairs are analyzed. The model considered assumes arbitrary value of the on-site density interaction of d-electrons U d , which allows investigation of the effects of reduced d-pair binding energy. The phase diagrams of the system have been evaluated within the approach which treats the on-site interaction term U d exactly and the remaining interactions within the broke symmetry HFA. Within the linear response theory the electromagnetic kernels are calculated and basic superfluid characteristics of the system are determined as a function of electron concentration, interactions and relative position of the bands. Depending on parameters the model is found to exhibit several kinds of superconducting behaviors ranging from the BCS-like to the local pair-like. The relevance of obtained results to the interpretation of experimental data for short-coherence length superconductors is pointed out.

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Stefański, Piotr. "The role of phase coherence length in electron transport through a Kondo double quantum dot interferometer with Rashba interaction." physica status solidi (b) 251, no. 3 (October 28, 2013): 633–41. http://dx.doi.org/10.1002/pssb.201350066.

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Rack, A., M. Scheel, L. Hardy, C. Curfs, A. Bonnin, and H. Reichert. "Exploiting coherence for real-time studies by single-bunch imaging." Journal of Synchrotron Radiation 21, no. 4 (May 9, 2014): 815–18. http://dx.doi.org/10.1107/s1600577514005852.

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First real-time studies of ultra-fast processes by single-bunch imaging at the European Synchrotron Radiation Facility are reported. By operating the storage ring of the ESRF in single-bunch mode with its correspondingly increased electron bunch charge density per singlet, the polychromatic photon flux density at insertion-device beamlines is sufficient to capture hard X-ray images exploiting the light from a single bunch (the corresponding bunch length is 140 ps FWHM). Hard X-ray imaging with absorption contrast as well as phase contrast in combination with large propagation distances is demonstrated using spatial samplings of 11 µm and 35 µm pixel size. The images acquired allow one to track crack propagation in a bursting piece of glass, breaking of an electrical fuse as well as cell wall rupture in an aqueous foam. Future developments and their potential in the frame of the proposed Phase II of the ESRF Upgrade Program are discussed.

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Islam, Saiful, Johan Stiens, Gert Poesen, Irina Jaeger, and Roger Vounckx. "Passive Frequency Selective Surface Array as a Diffuser for Destroying Millimeter Wave Coherence." Active and Passive Electronic Components 2008 (2008): 1–6. http://dx.doi.org/10.1155/2008/391745.

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This paper presents the design, construction, and testing of grounded frequency selective surface (FSS) array as a diffuser for destroying millimeter wave coherence which is used to eliminate speckle in active millimeter wave imaging. To create stochastically independent illumination patterns, we proposed a diffuser based on random-phase distributions obtained by changing the incident frequency. The random-phase diffuser was obtained by mixing up the phase relations between the cells of a deterministic function (e.g., beam splitter). The slot length of FSS is the main design parameter used to optimize the phase shifting properties of the array. The critical parameters of the diffuser array design, such as phase relation with slot lengths, losses, and bandwidth, are discussed. We designed the FSS arrays with finite integral technique (FIT), fabricated by etching technique, and characterized theS-parameters with a free-space MVNA, and measured the radiation patterns with a BWO in motorized setup.

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Chatterjee, Abhijit, Shashidhara Acharya, and S. M. Shivaprasad. "Morphology-Related Functionality in Nanoarchitectured GaN." Annual Review of Materials Research 50, no. 1 (July 1, 2020): 179–206. http://dx.doi.org/10.1146/annurev-matsci-081919-014810.

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Integrating silicon and III-nitride technologies for high-speed and large bandwidth communication demands optically interconnected active components that detect, process, and emit photons and electrons. It is imperative that multifunctional materials can enhance the performance and simplify fabrication of such devices. Spontaneously grown GaN in the nanowall network (NwN) architecture simultaneously displays unprecedented optical and electrical properties. A two-order increase in band-edge emission makes it suitable for high-brightness light-emitting diodes and laser applications. Decorating this NwN with silver nanoparticles further enhances emission through plasmonic interactions and renders it an excellent surface-enhanced Raman spectroscopy substrate for biomolecular detection. The observation of very high electron mobility (approximately 104 cm2/Vs) and large phase-coherence length (60 μm) is a consequence of two-dimensional (2D) electron gas formation applicable for high electron mobility transistors. Detecting ballistic transport in the nanowalls confirms proximity-induced superconductivity (<5 K and 8 T). Charge separation properties render it a device material for UV photodetectors, photoanodes for water splitting, and thermionic field emitters.

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Mohammed, N. H., A. I. Abou-Aly, M. ME Barakat, and M. S. Hassan. "Effect of nano BiPb-2212 phase addition on BiPb-2223 phase properties." Modern Physics Letters B 32, no. 16 (June 5, 2018): 1850178. http://dx.doi.org/10.1142/s0217984918501786.

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BiPb-2212 phase in nanoscale was added to BiPb-2223 phase with a general stoichiometry of (Bi[Formula: see text]Pb[Formula: see text]Sr[Formula: see text]Ca[Formula: see text]Cu[Formula: see text]O[Formula: see text]/Bi[Formula: see text]Pb[Formula: see text]Sr[Formula: see text]Ca[Formula: see text]Cu[Formula: see text]O[Formula: see text], 0.0 [Formula: see text] x [Formula: see text] 2.5 wt.%. All samples were prepared by the standard solid-state reaction method. The prepared nano BiPb-2212 phase was characterized by X-ray powder diffraction (XRD) and transmission electron microscope (TEM). The prepared samples were characterized by XRD and the scanning electron microscope (SEM). XRD analysis indicated that the sample with x = 1.5 wt.% has the highest relative volume fraction for BiPb-2223 phase. Samples were examined by electrical resistivity and I–V measurements. There is no significant change in the superconducting transition temperature [Formula: see text] for all samples. The highest critical current density [Formula: see text] was recorded for the sample with x = 1.5 wt.%. The normalized excess conductivity [Formula: see text] was calculated according to Aslamazov–Larkin (AL) model. Four different fluctuating regions were recorded as the temperature decreased. The coherence length along the c-axis at 0 K [Formula: see text], interlayer coupling strength s, Fermi velocity [Formula: see text] of the carriers and Fermi energy [Formula: see text] were calculated for both samples with x = 0.0 wt.% and 1.5 wt.%.

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Singh, Udai R., Seth C. White, Stefan Schmaus, Vladimir Tsurkan, Alois Loidl, Joachim Deisenhofer, and Peter Wahl. "Evidence for orbital order and its relation to superconductivity in FeSe0.4Te0.6." Science Advances 1, no. 9 (October 2015): e1500206. http://dx.doi.org/10.1126/sciadv.1500206.

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The emergence of nematic electronic states accompanied by a structural phase transition is a recurring theme in many correlated electron materials, including the high-temperature copper oxide– and iron-based superconductors. We provide evidence for nematic electronic states in the iron-chalcogenide superconductor FeSe0.4Te0.6 from quasi-particle scattering detected in spectroscopic maps. The symmetry-breaking states persist above Tc into the normal state. We interpret the scattering patterns by comparison with quasi-particle interference patterns obtained from a tight-binding model, accounting for orbital ordering. The relation to superconductivity and the influence on the coherence length are discussed.

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Wong, Chi Ho, Frank L. Y. Lam, Junying Shen, Minquan He, Xijun Hu, and Rolf Lortz. "The role of the coherence length for the establishment of global phase coherence in arrays of ultra-thin superconducting nanowires." Superconductor Science and Technology 30, no. 10 (September 12, 2017): 105004. http://dx.doi.org/10.1088/1361-6668/aa80d1.

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Baik, Jihye, Junbum Park, Gyeongjun Lee, Sungchul Kim, and Jungho Kim. "Effects of Incoherent Front Cover Glass on Current-Voltage Characteristics of Cu(In,Ga)Se2 Solar Cells: Investigation into Calculation Accuracy for Cover Glass Modeled as Optically Coherent or Incoherent." Applied Sciences 10, no. 9 (May 9, 2020): 3312. http://dx.doi.org/10.3390/app10093312.

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We numerically investigate the effects of an incoherent front cover glass on the current–voltage (J–V) characteristics of a Cu(In,Ga)Se2 (CIGS) solar cell using an integrated optoelectronic model. A 3-mm cover glass—the thickness of which was larger than the coherence length of sunlight—was incoherently modeled based on the equispaced thickness averaging method, where coherent simulation results of the wave equation were averaged over a set of equispaced phase thicknesses. The changes in optical power dissipation, absorptivity and electron–hole pair generation rate were calculated depending on the variation of the equispaced phase thickness. The calculation results of the J–V curves were obtained through numerical solutions of the coupled Poisson and continuity equations. By comparing the J–V curves calculated between coherently and incoherently modeled cover glass, we obtained a maximum ±0.54% deviation of the short-circuit current density. This demonstrates that the front cover glass should be modeled as optically incoherent to improve the calculation accuracy of the electrical J–V curves as well as the optical absorption characteristics in the optoelectronic modeling of CIGS solar cells.

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BERGER, V. "SECOND HARMONIC GENERATION USING A NON BIREFRINGENT MATERIAL IN A DOUBLY RESONANT MONOLITHIC CAVITY." Journal of Nonlinear Optical Physics & Materials 05, no. 03 (July 1996): 591–601. http://dx.doi.org/10.1142/s0218863596000416.

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Doubly resonant second harmonic generation (SHG) in a monolithic cavity is theoretically analysed. Using a non birefringent material as non linear medium, it is shown that both the double resonance condition and the phase matching condition between the two counter propagating second harmonic intracavity waves can be satisfied with a cavity length equal to the coherence length of the non linear process, and with well designed mirror phases. It is also shown theoretically how the double resonance can be maintained with only one tuning parameter. A SHG cavity enhancement of a few tens of thousands may be achieved at double resonance.

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Hatem, O. "Optimizing the electro-optic detection of terahertz waves by ZnTe at 780 and 1560-nm probe-beam wavelengths." Journal of Nonlinear Optical Physics & Materials 27, no. 04 (December 2018): 1850043. http://dx.doi.org/10.1142/s0218863518500431.

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Investigations were made for optimizing ZnTe as a THz detector at 1560-nm probe beam wavelength, and was compared with its performance at 780[Formula: see text]nm. High-sensitive THz detection was achieved when phase matching was maintained for long coherence lengths between the probe beam and the incident THz waves. A 1-mm thick ZnTe crystal enabled detection bandwidths of THz radiation up to 2 and 3 THz with probe wavelengths at 1560 and 780[Formula: see text]nm, respectively. Theoretical calculations showed coherence length of less than 50[Formula: see text][Formula: see text]m in ZnTe between the THz wave components above 4 THz and the optical waves at 780 and 1560[Formula: see text]nm.

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Kapcia, Konrad. "Metastability and Phase Separation in a Simple Model of a Superconductor with Extremely Short Coherence Length." Journal of Superconductivity and Novel Magnetism 27, no. 4 (November 14, 2013): 913–17. http://dx.doi.org/10.1007/s10948-013-2409-8.

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Kim, Jihoon, Junghwan Oh, and Thomas E. Milner. "Measurement of optical path length change following pulsed laser irradiation using differential phase optical coherence tomography." Journal of Biomedical Optics 11, no. 4 (2006): 041122. http://dx.doi.org/10.1117/1.2236289.

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Suphakul, Sikharin, Heishun Zen, Toshiteru Kii, and Hideaki Ohgaki. "Investigation of Bunch Compressor and Compressed Electron Beam Characteristics by Coherent Transition Radiation." Particles 2, no. 1 (December 31, 2018): 32–43. http://dx.doi.org/10.3390/particles2010003.

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A magnetic chicane bunch compressor for a new compact accelerator-based terahertz (THz) radiation source at the Institute of Advanced Energy, Kyoto University, was completely installed in March 2016. The chicane is employed to compress an electron bunch with an energy of 4.6 MeV generated by a 1.6-cell photocathode radio frequency (RF)-gun. The compressed bunch is injected into a short planar undulator for THz generation by coherent undulator radiation (CUR). The characteristics of the bunch compressor and the compressed bunch were investigated by observing the coherent transition radiation (CTR). The CTR spectra, which were analyzed by using a Michelson interferometer, and the compressed bunch length were also estimated. The results were that the chicane could compress the electron bunch at a laser injection phase less than 45 degrees, and the maximum CTR intensity was observed at a laser injection phase around 24 degrees. The optimum value of the first momentum compaction factor was around −45 mm, which provided an estimated rms bunch length less than 1 ps.

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Freethy, Simon J., Tobias Görler, Alex J. Creely, Garrard D. Conway, Severin S. Denk, Tim Happel, Pascale Henniquin, Christian Koenen, and Anne E. White. "Advances in turbulence measurements using new Correlation ECE and nT-phase diagnostics at ASDEX Upgrade." EPJ Web of Conferences 203 (2019): 03001. http://dx.doi.org/10.1051/epjconf/201920303001.

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Guided by predictions from nonlinear gyrokinetic simulations, two new turbulence diagnostics were designed and installed at ASDEX Upgrade (AUG) to probe the fundamentals of ion-scale turbulent electron heat transport. The first, a 30-channel correlation ECE (CECE) radiometer (105-128 GHz, 2nd harmonic X-mode), introduces a novel channel comb arrangement. This allows measurements of high radial resolution profiles (0:5 < r/a < 0:8) of low-k (k⍬⍴s < 0:3) temperature fluctuation amplitudes, frequency spectra and radial correlation length profiles in unprecedented detail. The second diagnostic is formed by the addition of two W-band and one V-band X-mode reflectometers on the same line of sight as the CECE to enable measurements of the phase angle between turbulent density and temperature fluctuations. Historically, the radial alignment between reflectometer and radiometer has been a challenge due to the requirement that alignment is achieved within a radial correlation length (< 5 10 mm). This challenge is significantly alleviated by using the CECE channel comb arrangement and the maximal coherence between reflectometer and radiometer can be unambiguously captured. Measurements of these quantities have been made in an AUG L-mode plasma, at the same radial location and have provided simultaneous quantitative constraints on realistic gyrokinetic simulations [Physics of Plasmas 25, 055903 (2018)] using the gyrokinetic code GENE. Here we present diagnostic detail for this study.

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Machida, Masahiko, and Mitsuhiro Itakura. "Phase and amplitude fluctuations above the upper critical field in type II superconductors with short coherence length." Physica C: Superconductivity 412-414 (October 2004): 333–37. http://dx.doi.org/10.1016/j.physc.2003.12.044.

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Varghese, Babu, Vinayakrishnan Rajan, Ton G. Van Leeuwen, and Wiendelt Steenbergen. "High angle phase modulated low coherence interferometry for path length resolved Doppler measurements of multiply scattered light." Optics Communications 281, no. 3 (February 2008): 494–98. http://dx.doi.org/10.1016/j.optcom.2007.09.050.

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Huang, Zheng. "Rashba Spin-Orbit Effect on Traversal Time in Parabolic-Well Magnetic Tunneling Junction." Applied Mechanics and Materials 707 (December 2014): 338–42. http://dx.doi.org/10.4028/www.scientific.net/amm.707.338.

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Based on the phase time definition,we study theoretically the transmission coefficients and the spin-tunneling time in parabolic-well magnetic tunneling junction with a tunnel barrier in the presence of Rashba spin-orbit interaction. The significant quantum size, quantum coherence, and Rashba spin-orbit interaction are considered simultaneously. It is found that the tunneling time strongly depends on the spin orientation of tunneling electrons. We also find that as the length of the semiconductor increases, the spin tunneling time shows curved increase. It exhibits useful instructions for the design of spin electronic devices.

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Nishio, Rimi, Toyohiko J. Konno, and Satoshi Semboshi. "Transmission Electron Microscopy Observations on Cu-Ti Alloy Systems." Materials Science Forum 502 (December 2005): 163–68. http://dx.doi.org/10.4028/www.scientific.net/msf.502.163.

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Phase separation behaviors of a quenched Cu-3.0at%Ti alloy, as well as crystallographic structures of Cu-20.7at%Ti alloy have been studied using transmission electron microscopy. The furnacecooled Cu-20.7at%Ti alloy are composed of a-Cu4Ti (Ni4Mo-type) and b-Cu4Ti (Au4Zr-type) with the orientation relationship of (011)a//(110)b, [100]a//[001]b. As-quenched Cu-3.0at%Ti alloy showed a modulated structure with the modulation length of about 4 nm. When aged at 723K for 8 hr, the a-Cu4Ti phase emerges within the modulated or tweed-like microstructure. Prolonged aging results in the growth of the a-Cu4Ti particles and the loss of coherency. It is likely that asquenched Cu-3.0at%Ti alloy decomposes spinodally at 723K, followed by polymorphous ordering; though the present study did not exclude, as an alternative path, a decomposition mechanism based on the catastrophic nucleation.

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KRISTOFFEL, NIKOLAI, PAVEL RUBIN, and TEET ÖRD. "MULTIBAND MODEL OF CUPRATE SUPERCONDUCTIVITY." International Journal of Modern Physics B 22, no. 30 (December 10, 2008): 5299–327. http://dx.doi.org/10.1142/s0217979208049443.

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A minimal model for the description of cuprate superconductor characteristics on doping scale (hole and electron) is developed. The leading interband pairing channel couples an itinerant band and defect states created by doping. Bare gaps between them are supposed and become closed by extended doping. Band overlap conditions determine special points in the phase diagram. Nodal and antinodal momentum regions are distinguished. Illustrative calculations have been made using a mean-field pair-transfer multiband Hamiltonian and corresponding free-energy expansions. The results are self-consistent and demonstrate that the elaborated approach is able to reproduce characteristic features of cuprate superconductors as, e.g., the doping dependence of Tc, superconducting gaps and pseudogaps, supercarrier density and effective mass, coherence length and penetration depth, critical magnetic fields and some other properties. Interband pairing scheme is suggested to be an essential aspect of cuprate superconductivity.

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Babcock, S. E., T. F. Kelly, and D. C. Larbalestier. "High-resolution analytical microscopy of YBa2Cu3O7-δ grain boundaries." Proceedings, annual meeting, Electron Microscopy Society of America 47 (August 6, 1989): 194–95. http://dx.doi.org/10.1017/s042482010015294x.

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Grain boundaries are generally considered to be the microstructural entity which is responsible for the weak-link behavior that limits the transport critical current densities (Jct) of the high temperature oxide superconductors to values which are unacceptable for most applications. However, the mechanism by which grain boundaries suppress Jct has yet to be identified. This issue is particularly challenging because the microstructural features which affect Jct may be as small as the superconducting coherence length (< 1 nm for the high-temperature superconductors). Electron microscopy studies, nevertheless, have suggested a number of possible microstructural origins for the weak-link behavior. Among the candidates are: the strains associated with grain boundary dislocations; segregated impurity atoms layers of second phase; and local (within ∼ 5 nm) composition changes at grain boundaries which involve a reduction in the oxygen atom fraction.

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Li, Yinan, Markus Kästner, and Eduard Reithmeier. "Optimization of the GPU-based data evaluation for the low coherence interferometry." tm - Technisches Messen 85, no. 11 (November 27, 2018): 680–90. http://dx.doi.org/10.1515/teme-2017-0091.

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Abstract Optical interferometers as non-contact measurement devices are very desirable for the measurement of surface roughness and topography. Compared to phase shifting interferometers (PSIs) with a limited measurement range and a scan step of maximum λ/4, the optical interferometers like low coherence interferometers (LCIs) evaluating the degree of fringe coherence allow a larger vertical measurement range. Their vertical measurement range is only limited by the scan length allowed by the linear piezo stage and the coherence length of the light source. To evaluate the obtained data for a large range, the common LCIs require much computation time. To overcome this drawback, we present an evaluation algorithm based on the Hilbert-Transform and curve fitting (Levenberg–Marquardt algorithm) using Compute Unified Device Architecture (CUDA) technology, which allows parallel and independent data evaluation on General Purpose Graphics Processing Unit (GPGPU). Firstly, the evaluation algorithm is implemented and tested on an in-house developed LCI, which is based on Michelson configurations. Furthermore, we focus on the performance optimization of the GPU-based program using the different approaches to further achieve efficient and accurate massive parallel computing. Finally, the performance comparison for evaluating measurement data using different approaches is discussed in this paper.

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Falabella, Francesco, Carmine Serio, Giovanni Zeni, and Antonio Pepe. "On the Use of Weighted Least-Squares Approaches for Differential Interferometric SAR Analyses: The Weighted Adaptive Variable-lEngth (WAVE) Technique." Sensors 20, no. 4 (February 18, 2020): 1103. http://dx.doi.org/10.3390/s20041103.

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This paper concentrates on the study of the Weighted Least-squares (WLS) approaches for the generation of ground displacement time-series through Differential Interferometric SAR (DInSAR) methods. Usually, within the DInSAR framework, the Weighted Least-squares (WLS) techniques have principally been applied for improving the performance of the phase unwrapping operations as well as for better conveying the inversion of sequences of unwrapped interferograms to generate ground displacement maps. In both cases, the identification of low-coherent areas, where the standard deviation of the phase is high, is requested. In this paper, a WLS method that extends the usability of the Multi-Temporal InSAR (MT-InSAR) Small Baseline Subset (SBAS) algorithm in regions with medium-to-low coherence is presented. In particular, the proposed method relies on the adaptive selection and exploitation, pixel-by-pixel, of the medium-to-high coherent interferograms, only, so as to discard the noisy phase measurements. The selected interferometric phase values are then inverted by solving a WLS optimization problem. Noteworthy, the adopted, pixel-dependent selection of the “good” interferograms to be inverted may lead the available SAR data to be grouped into several disjointed subsets, which are then connected, exploiting the Weighted Singular Value Decomposition (WSVD) method. However, in some critical noisy regions, it may also happen that discarding of the incoherent interferograms may lead to rejecting some SAR acquisitions from the generated ground displacement time-series, at the cost of the reduced temporal sampling of the data measurements. Thus, variable-length ground displacement time-series are generated. The mathematical framework of the developed technique, which is named Weighted Adaptive Variable-lEngth (WAVE), is detailed in the manuscript. The presented experiments have been carried out by applying the WAVE technique to a SAR dataset acquired by the COSMO-SkyMed (CSK) sensors over the Basilicata region, Southern Italy. A cross-comparison analysis between the conventional and the WAVE method has also been provided.

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Jin, Long, Zirui Zhang, Nuo Wang, Zixin Liu, Yuwei Deng, and Yanhua Fu. "Intensity Distribution of Partially Coherent Array Finite Airy Beams Propagating in Atmospheric Turbulence." International Journal of Optics 2021 (February 5, 2021): 1–11. http://dx.doi.org/10.1155/2021/6649144.

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Based on the extended Huygens–Fresnel integral and the Rytov phase structure function, the closed-form expression of a partially coherent array finite Airy beams (PCAFABs) cutting through the Kolmogorov atmospheric turbulence is derived in the space domain under the paraxial approximation. The characteristics of the PCAFABs evoluting in the atmospheric environment are investigated in detail on the basis of the derived wave propagation formulae. We mainly illustrate the intensity profile of this beam changed with the truncation parameter, coherence length, and turbulence factor at several cross sections of the atmospheric space by means of numerical figures. It is convinced that the present concept and derived conclusions will provide useful exploration for learning the optical properties of the PCAFABs transmitting in the atmospheric turbulence, especially for free-space optical communication area.

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Bonevich, J., D. Capacci, G. Pozzi, K. Harada, H. Kasai, T. Matsuda, and A. Tonomura. "On the influence of specimen thickness in TEM images of super-conducting vortices." Proceedings, annual meeting, Electron Microscopy Society of America 54 (August 11, 1996): 724–25. http://dx.doi.org/10.1017/s0424820100166087.

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The successful observation of superconducting flux lines (fluxons) in thin specimens both in conventional and high Tc superconductors by means of Lorentz and electron holography methods has presented several problems concerning the interpretation of the experimental results. The first approach has been to model the fluxon as a bundle of flux tubes perpendicular to the specimen surface (for which the electron optical phase shift has been found in analytical form) with a magnetic flux distribution given by the London model, which corresponds to a flux line having an infinitely small normal core. In addition to being described by an analytical expression, this model has the advantage that a single parameter, the London penetration depth, completely characterizes the superconducting fluxon. The obtained results have shown that the most relevant features of the experimental data are well interpreted by this model. However, Clem has proposed another more realistic model for the fluxon core that removes the unphysical limitation of the infinitely small normal core and has the advantage of being described by an analytical expression depending on two parameters (the coherence length and the London depth).

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Shoucri, Magdi. "Formation of electron holes in the long-time evolution of the bump-on-tail instability." Laser and Particle Beams 35, no. 4 (December 2017): 706–21. http://dx.doi.org/10.1017/s0263034617000775.

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AbstractAn Eulerian Vlasov code is applied for the numerical solution of the one-dimensional Vlasov–Poisson system of equations for electrons, and with ions forming an immobile background. We study the non-linear evolution of the bump-on-tail instability in the case when the system length L is greater than the wavelength λ of the unstable mode, with a beam density of 10% of the total density, nb = 0.1. We follow the growth and the saturation of an initially unstable wave perturbation, and the formation of a traveling Bernstein–Greene–Kruskal (BGK) mode, which evolves out of the instability. This first stage is followed by sidebands growing from round-off errors which develop and disrupt the BGK equilibrium. In the excited spectrum, mode coupling is mediated by the oscillating resonant particles and results in the electric energy of the system flowing to the longest wavelengths (inverse cascade), and reaching in the asymptotic state a steady state with constant amplitude oscillation modulated by the persistent oscillation of the trapped particles. Coherent phase-space electron holes are formed, which are localized phase-space regions of reduced density on trapped electron orbits, where the electron density is lower than the surrounding plasma electron density. The distribution function evolves to a shape with stationary inflection points of zero slope, at the phase velocities of the excited waves. The longest wavelengths show oscillations at frequencies below the plasma frequency, with phase velocities higher than that of the injected beam, which can accelerate electrons to energies in excess of the initial beam energy. The present work makes a connection between the formation of electron holes, the existence of inflection points of zero slopes in the electron distribution function at the phase velocities of the dominant waves, and at frequencies below the plasma frequency. A fine resolution grid is used in the Eulerian Vlasov code in the phase space and time to allow an accurate calculation of the time history of the system and of the dynamic and oscillation of the trapped particles in the low-density regions of the phase space, and of those particles at the separatrix regions of the vortex structures which evolve periodically between trapping and untrapping states and which can only be accurately studied using a fine-resolution phase-space grid.

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Nishikawa, Ken Ichi, Satoshi Semboshi, and Toyohiko J. Konno. "Transmission Electron Microscopy Observations on Cu-Mg Alloy Systems." Solid State Phenomena 127 (September 2007): 103–8. http://dx.doi.org/10.4028/www.scientific.net/ssp.127.103.

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Environmentally friendly Cu-based alloys with high strength and low electrical resistivity have been much sought in order to replace deleterious Cu-Be alloys for electrical applications. As one of the candidate systems, we have examined age-hardening behaviors of Cu-Mg alloys by using transmission electron microscopy (TEM). Cu-2.26wt.%Mg alloys were solution-treated and annealed at 723K, and their structural changes have been investigated. The Vickers hardness measurements showed that they aged-harden gradually. Our TEM observations showed that annealing for 6h brings about precipitation of numerous needle-like particles of 10 nm in length. The diffraction studies indicated these precipitates consist of the Cu2Mg phase with {111}Cu habit planes. When annealed for 96h, these precipitates become semi-coherent, which was manifested by moiré fringes; while maintaining the orientation relationship of (111)Cu//(111)Cu2Mg, [110]Cu//[110]Cu2Mg.

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Ashoka, A., Bhagyashree K. S., and S. V. Bhat. "Magnetic Field Induced Berezinskii-Kosterlitz-Thouless Correlations in 3-Dimensional Manganites." MRS Advances 5, no. 44 (2020): 2251–60. http://dx.doi.org/10.1557/adv.2020.320.

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AbstractIdeal two-dimensional (2D) Heisenberg magnets lack long range magnetic order. However, the XY model with spins confined to a plane shows a topological phase transition at a finite temperature corresponding to binding and unbinding of vortices. Experimental evidence for such Berezinskii-Kosterlitz-Thouless (BKT) transitions has been difficult to obtain in condensed matter systems, where, even a weak interlayer coupling that is invariably present leads to long-range order, pre-empting the BKT transition. The BKT signatures are still discernible above the long-range ordering temperature, however, in the characteristic exponential temperature dependence of the coherence length of the fluctuations. In this work we report that an applied magnetic field can induce such BKT correlations not only in quasi 2-dimensional systems but also in nominally 3-dimensional manganites undergoing antiferromagnetic transitions. We arrive at this unexpected conclusion based on our studies of temperature dependence of electron paramagnetic resonance (EPR) linewidth ΔH(T) of Cr3+ doped bismuth strontium manganite Bi0.5Sr0.5Mn1-xCrxO3 (x= 0.04, 0.1) (BSMCO04 and BSMCO10).

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46

Varghese, Babu, Vinayakrishnan Rajan, Ton G. Van Leeuwen, and Wiendelt Steenbergen. "Path-length-resolved measurements of multiple scattered photons in static and dynamic turbid media using phase-modulated low-coherence interferometry." Journal of Biomedical Optics 12, no. 2 (2007): 024020. http://dx.doi.org/10.1117/1.2714795.

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Marychev, Pavel M., and Denis Yu Vodolazov. "A Josephson junction based on a highly disordered superconductor/low-resistivity normal metal bilayer." Beilstein Journal of Nanotechnology 11 (June 2, 2020): 858–65. http://dx.doi.org/10.3762/bjnano.11.71.

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We calculate the current–phase relation (CPR) of a SN-S-SN Josephson junction based on a SN bilayer of variable thickness composed of a highly disordered superconductor (S) and a low-resistivity normal metal (N) with proximity-induced superconductivity. In such a junction, the N layer provides both a large concentration of phase in the weak link and good heat dissipation. We find that when the thickness of the S and the N layer and the length of the S constriction are about the superconducting coherence length the CPR is single-valued and can be close to a sinusoidal shape. The product I c R n can reach Δ(0)/2|e| (I c is the critical current of the junction, R n is its normal-state resistance, Δ(0) is the superconductor gap of a single S layer at zero temperature). Our calculations show, that the proper choice of the thickness of the N layer leads both to nonhysteretic current–voltage characteristics even at low temperatures and a relatively large product I c R n.

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THOMPSON, M. C., H. BADAKOV, J. B. ROSENZWEIG, G. TRAVISH, M. HOGAN, R. ISCHEBECK, N. KIRBY, et al. "PRELIMINARY RESULTS FROM THE UCLA/SLAC ULTRA-HIGH GRADIENT CERENKOV WAKEFIELD ACCELERATOR EXPERIMENT." International Journal of Modern Physics A 22, no. 23 (September 20, 2007): 4343–54. http://dx.doi.org/10.1142/s0217751x07037883.

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The first phase of an experiment to study the performance of dielectric Cerenkov wakefield accelerating structures at extremely high gradients in the GV/m range has been completed. This experiment takes advantage of the unique SLAC FFTB electron beam and its demonstrated ultra-short pulse lengths and high currents (e.g., σz = 20 μ m at Q = 3 nC ). The FFTB electron beam has been successfully focused down and sent through varying lengths of fused silica capillary tubing with two different sizes: ID = 200 μ m / OD = 325 μ m and ID = 100 μ m / OD = 325 μ m . The pulse length of the electron beam was varied in the range 20 μ m < σz < 100 μ m which produced a range of electric fields between 2 and 20 GV/m at the inner surface of the dielectric tubes. We observed a sharp increase in optical emissions from the capillaries in the middle part of this surface field range which we believe indicates the transition between sustainable field levels and breakdown. If this initial interpretation is correct, the surfaced fields that were sustained equate to on axis accelerating field of several GV/m. In future experiments we plan to collect and measure coherent Cerenkov radiation emitted from the capillary tube to gain more information about the strength of the accelerating fields.

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CHIANG, Yu N., and O. G. SHEVCHENKO. "PHASE–SENSITIVE ANDREEV CONDUCTANCE OF AN SNS SYSTEM WITH THE SUPPRESSED PROXIMITY EFFECT." International Journal of Modern Physics B 19, no. 01n03 (January 30, 2005): 131–33. http://dx.doi.org/10.1142/s0217979205028074.

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A study is made of the dissipative component of the electron transport in a doubly connected Andreev SNS interferometer with elastic mean free paths lel in the metals of around 100μ m and a macroscopic phase–breaking length [Formula: see text] which is two or more orders of magnitude larger than [Formula: see text] in disordered nanostructures. At helium temperatures, the samples are found to exhibit new phase–sensitive effects of a quantum–interference nature. Below 2 K , the conductance of the macroscopic N region of the system has an oscillatory component of resonance shape which undergoes the phase inversion relative to the phase of the nonresonance oscillations. An explanation for the effects is suggested in terms of the contribution to the Josephson current from coherent quasiparticles with energies of order of the Thouless energy. The temperature behavior of the dissipative transport in a pure normal metal near an isolated NS point contact is studied.

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Судоргин, С. А., and Н. Г. Лебедев. "Дифференциальная термоЭДС углеродных нанотрубок типа "zigzag" во внешнем электрическом поле." Физика твердого тела 62, no. 10 (2020): 1710. http://dx.doi.org/10.21883/ftt.2020.10.49926.055.

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The influence of (0.00, 0.20, 0.40, 0.50, and 0.60wt%) nano-sized tin oxide (SnO2) particles on electrical conductivity fluctuation in normal and superconducting state of the Y3Ba5Cu8O18±δ (denoted as Y-358) polycrystalline samples is studied. Phase formation and microstructures have been systematically examined. By increasing the content of SnO2 in YBCO matrix, X-ray diffraction technique showed slightly variation in lattice parameters and overall reduction in the orthorhombicity. Scanning electron microscopy observations and the crystallite size calculation also revealed that the grain size and the average crystallite size decreased compared to the SnO2 free sample. Aslamazov–Larkin and Lawrence–Doniach prototypes were performed to analyse conductivity fluctuations based on the electrical resistivity ρ(T) measurements. Superconducting transition temperatures Tc and TLD have been reported. The influence of SnO2 addition on the superconducting properties indicates that with the addition of SnO2 nanoparticles into Y-358 compound, some parameters values such as zero-resistance critical temperature Tc zero, coherence distance alongside the c axis at 0K ξc(0), and super-layer length d decrease in total, while anisotropy γ, critical magnetic fields Bc1(0), Bc2(0), and critical current density Jc(0) increase in SnO2-added Y-358 specimens compared to the pure one. The reasons corresponding to these scenarios are discussed in details.

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Journal articles on the topic 'Electron phase coherence length'

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