Дисертації з теми "Distinct charge density wave"
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Gaspar, Luis Alejandro Ladino. "CHARGE DENSITY WAVE POLARIZATION DYNAMICS." UKnowledge, 2008. http://uknowledge.uky.edu/gradschool_diss/643.
Повний текст джерелаRai, Ram C. "ELECTRO-OPTICAL STUDIES OF CHARGE-DENSITY-WAVE MATERIALS." UKnowledge, 2004. http://uknowledge.uky.edu/gradschool_diss/427.
Повний текст джерелаRu, Nancy. "Charge density wave formation in rare-earth tritellurides /." May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
Повний текст джерелаHite, Omar. "Controlling the Charge Density Wave in VSE2 Containing Heterostructures." Thesis, University of Oregon, 2018. http://hdl.handle.net/1794/23179.
Повний текст джерелаBoshoff, Ilana. "Ultrafast electron diffraction on the charge density wave compound 4Hb-TaSe2." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/20062.
Повний текст джерелаENGLISH ABSTRACT: Ultrafast electron diffraction is a powerful method to study atomic movement in crystals on sub-picosecond timescales. This thesis consists of three parts. In part one the ultrafast electron diffraction machine is described, followed by improvements that were made and techniques that were developed in order to bring the system to state of the art level and enable the acquisition of suffcient data to obtain information on the structural dynamics in crystals. The second part contains a description of the sample which was studied in our fi rst time-resolved measurements, the transition-metal dichalcogenide 4Hb-TaSe2. This particular crystal is an example of a strongly coupled electronic system which develops a charge density wave (CDW) accompanied by a periodic lattice distortion (PLD). An overview of the formation of electron diffraction patterns and what can be learned from them are also given, followed by the results of the ultrafast electron diffraction experiments done with 4Hb-TaSe2. Part three describes an alternative source to study dynamics in crystalline samples, namely laser plasma-based ultrafast X-ray diffraction. The ultrafast electron diffraction group functions as a unit, but my tasks ranged from sample preparation and characterisation of the electron beam to the setting up and execution of experiments. I was involved in analysing the data and contributed small parts to the data analysis software.
AFRIKAANSE OPSOMMING: Ultravinnige elektron diffraksie is a metode om die beweging van atome in kristalle op sub-pikosekonde tydskale te bestudeer. Hierdie tesis bestaan uit drie dele. In deel een van die tesis word die ultravinnige elektron diffraksie masjien beskryf, gevolg deur verbeteringe wat aangebring is en tegnieke wat ontwikkel is om die sisteem tot op 'n wêreldklas vlak te bring waar die insameling van genoegsame data om inligting oor die strukturele dinamika in kristalle te bekom, moontlik is. Die tweede deel bevat 'n beskrywing van die monster wat in ons eerste tydopgeloste eksperimente gebruik is, naamlik die oorgangsmetaaldichalkogenied 4Hb-TaSe2. Hierdie kristal is 'n voorbeeld van 'n sterk gekoppelde elektroniese sisteem wat 'n ladingsdigtheid-golf en 'n gepaardgaande periodiese versteuring van die kristalrooster ontwikkel. 'n Oorsig van die formasie van elektron diffraksiepatrone en wat ons daaruit kan leer word ook gegee. Daarna word die resultate van die ultravinnige elektron diffraksie eksperimente wat op 4Hb-TaSe2uitgevoer is beskryf en bespreek. In deel drie word 'n alternatiewe metode om die dinamika in kristalmonsters te bestudeer, naamlik laser plasma-gebaseerde ultravinnige X-straal diffraksie, beskryf. Die ultravinnige elektron diffraksie groep funksioneer as 'n eenheid, maar my verantwoordelikhede het gestrek van die voorbereiding van monsters en die karakterisering van die elektron bundel tot die opstel en uitvoer van eksperimente. Ek was ook betrokke by die analisering van data en het dele van die data analise sagteware geskryf.
Yetman, Paul John. "Experimental studies on the size dependence of sliding charge-density wave phenomena." Thesis, University of Bristol, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.279769.
Повний текст джерелаRen, Yuhang. "Time-resolved optical studies of colossal magnetoresistance and charge -density wave materials." W&M ScholarWorks, 2003. https://scholarworks.wm.edu/etd/1539623421.
Повний текст джерелаBellec, Ewen. "Study of charge density wave materials under current by X-ray diffraction." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS437/document.
Повний текст джерелаThe main subject of this manuscript is the X-ray diffraction of charge density wave (CDW) materials. We studied the quasi-1D NbSe3 crystal and the quasi-2D TbTe3. Several large instruments facilities were used for this study, the ESRF synchrotron in Grenoble on the ID01 line and the LCLS free electron laser in Stanford. First, thanks to the coherence of the X-beam at LCLS, we were able to observe a loss of transverse coherence in NbSe3 when applying an electrical current above a certain threshold as well as a longitudinal compression of the CDW. Then, at the ESRF, we used an X-ray beam focused on the micrometer scale by a Fresnel zone plate to scan the CDW locally by diffraction on NbSe3 and on TbTe3. When a current is applied to the sample, we observed a transverse deformation indicating that the CDW is pinned on the sample surface in NbSe3. In the case of TbTe3, the CDW rotates under current showing a hysteresis cycle when one is continuously changing from positive to negative current. We have also observed in several regions, in TbTe3, the creation of localized irradiation defects inducing a compression-dilation of the CDW. In a last theoretical part, we show how the theory of electric transport in the CDW state by a train of charged solitons, as well as taking into account the CDW pinning on the surface of the sample that we have seen experimentally, allows us to understand several resistivity measurements, found in the literature, made on samples with different dimensions. Finally, we present several ideas for an explanation of the CDW pinning at the surfaces on a microscopic level and propose the hypothesis of a commensurate CDW on the surface (and incommensurate in volume)
Edkins, Stephen David. "Visualising the charge and Cooper pair density waves in cuprates." Thesis, University of St Andrews, 2016. http://hdl.handle.net/10023/9888.
Повний текст джерелаYi, Tianyou. "Modeling of dynamical vortex states in charge density waves." Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00768237.
Повний текст джерелаLatt, Kyaw Zin. "Manipulation of Molecular Charge Density Waves and Molecular Transport Systems." Ohio University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1557418915977344.
Повний текст джерелаRamakrishnan, Sitaram [Verfasser], and Smaalen Sander [Akademischer Betreuer] van. "Charge-density-wave ordering in three-dimensional metallic compounds / Sitaram Ramakrishnan ; Betreuer: Sander van Smaalen." Bayreuth : Universität Bayreuth, 2020. http://d-nb.info/1213348951/34.
Повний текст джерелаROMANIN, DAVIDE. "Electron-phonon interactions in low-dimensional carbon systems: superconductivity and charge-density waves." Doctoral thesis, Politecnico di Torino, 2021. http://hdl.handle.net/11583/2872341.
Повний текст джерелаRocha, Matthew Paul. "A high-resolution study of the electronic structure of NbSe3 in normal and charge density wave states with angle resolved photoemission spectroscopy /." view abstract or download file of text, 2003. http://wwwlib.umi.com/cr/uoregon/fullcit?p3113025//.
Повний текст джерелаTypescript. Includes vita and abstract. Includes bibliographical references (leaves 166-167). Also available for download via the World Wide Web; free to University of Oregon users.
Sellam, Mohamed Amine. "Competition between charge density wave and metallic/superconducting states in metastable 1T-TaS2 and 1T-VS2 synthesised under high pressure." Paris 6, 2011. http://www.theses.fr/2011PA066585.
Повний текст джерелаSouza, Valdeci Pereira Mariano de [UNESP]. "Estudo das propriedades elétricas não lineares de polímeros conjugados." Universidade Estadual Paulista (UNESP), 2003. http://hdl.handle.net/11449/91942.
Повний текст джерелаNeste trabalho, apresentamos um estudo experimental das propriedades elétricas não lineares de polímeros conjugados, como por exemplo, curvas I(V) não lineares para baixos valores de campo elétrico aplicado e existência de um campo elétrico de threshold. Investigamos o comportamento elétrico não linear em pastilhas prensadas de poli(3-metiltiofeno) (P3MT) oxidadas, obtidas através do processo de síntese eletroquímica. Das medidas elétricas realizadas, na faixa de temperatura (~9 K - ~297 K), os resultados experimentais obtidos: curvas I(V), condutividade versus freqüência e constante dielétrica versus freqüência, foram comparados com os diversos modelos teóricos existentes na literatura. Os dados obtidos em toda a faixa de temperatura mencionada mostraram boa concordância com a teoria de tunelamento para CDW (charge density wave deppining) proposta por J. Bardeen.
In this work, we present an experimental study of the non-linear electrical properties in conjugated polymers, as for example, non-linear I(V) curves at low electric fields and existence of a threshold electric field. We investigated the non linear electrical behavior of pressed pellets of poly(3-methilthiopene) (P3MT), which were obtained through electrochemical synthesis oxidized. From the electrical measurements, in the temperature range (~9K - ~297K), the experimental results: I(V) curves, conductivity versus frequency and dielectric constant versus frequency, were compared with the several theoretical models discussed in the literature. The data obtained in the whole temperature range have shown good agreement on the tunneling theory for CDW systems (charge density wave depinning) proposed by J. Bardeen.
Ren, Zhensong. "Combined neutron, transport and material based investigation in Ca₃Ir₄Sn₁₃." Thesis, Boston College, 2015. http://hdl.handle.net/2345/bc-ir:104538.
Повний текст джерелаThis dissertation investigates the cubic type II superconductor, Ca₃Ir₄Sn₁₃, discovered by Remeika and the coauthors more than 30 years ago. It was originally discovered be to a superconductor and later suggested to host ferromagnetic spin fluctuations, which lead to a peak-like anomaly in thermodynamic and transport measurements. Later detailed x-ray single crystal structural refinement associated the peak-like anomaly in transport and magnetization measurements with a charge density wave phase transition at the same temperature. The potential charge density wave phase transition T* can be suppressed either by pressure or chemical potential through substitution on the Ca and Ir site such that a temperature-pressure/composition phase diagram can be constructed. Upon investigating magnetism in this compound, polarized neutron scattering and μSR data from our group and other researchers did not reveal any magnetic order or magnetic spin fluctuations at the time scale of μSR . However, through the partial substitution of Ir by Rh, we realized a structural quantum critical point at ambient pressure with 30% of Ir substituted by Rh--providing the research community a valuable material's platform for studying the interplay between 3D charge density wave order and superconductivity. On the other hand, our surprising discovery of the weak HHL (L=odd) type of super-lattice peaks from neutron scattering led us to a tentative model of a distorted Ca sublattice in this material. The similarity of the lattice instabilites of the Remeika compound and A15 superconductors are discussed, which may give us more insight into its role in the formation of the superconducting phase
Thesis (PhD) — Boston College, 2015
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Physics
Saint-Lager, Marie-Claire. "Etude de la cohérence de phase des ondes de densité de charge." Grenoble 1, 1988. http://www.theses.fr/1988GRE10090.
Повний текст джерелаJurczek, Edmund. "A local charge density wave instability in alloys with strong electron phonon coupling with application to Ba Bi-(1-x) Pb-x 0-3 /." Zürich, 1985. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=7880.
Повний текст джерелаAl-Hadeethi, Ali Khairi Abdul-Qader [Verfasser], and Christine A. [Akademischer Betreuer] Kuntscher. "Dc transport and optical measurements on the charge-density-wave compounds (K,Rb)0.3(Mo,W)O3 / Ali Khairi Abdul-Qader Al-Hadeethi. Betreuer: Christine A. Kuntscher." Augsburg : Universität Augsburg, 2013. http://d-nb.info/107770285X/34.
Повний текст джерелаChen, Mengsu. "Exact diagonalization study of strongly correlated topological quantum states." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/87436.
Повний текст джерелаPHD
Topological quantum states are a new type of quantum state that have properties that cannot be described by local order parameters. These types of states were first discovered in the 1980s with the integer quantum Hall effect and the fractional quantum Hall effect. In the 2000s, the predicted and experimentally discovered topological insulators triggered studies of new topological quantum states. Studies of strongly correlated systems have been a parallel research topic in condensed matter physics. When combining topological systems with strong correlation, the resulting systems can have novel properties that emerge, such as fractional charge. This thesis summarizes our work that uses the exact diagonalization method to study topological states with strong interaction.
Erasmus, Nicolas. "Ultrafast structural dynamics in 4Hb-TaSe2 observed by femtosecond electron diffraction." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/79934.
Повний текст джерелаENGLISH ABSTRACT: In this thesis the structural dynamics, upon photo-excitation, of the charge-densitywave (CDW) material 4Hb-TaSe2 is investigated on the time-scale of atomic motion and simultaneously on the spatial-scale of atomic dimensions. CDW materials have been of interest since their discovery in the 1970’s because of their remarkable non-linear and anisotropic electrical properties, gigantic dielectric constants, unusual elastic properties and rich dynamical behaviour. Some of these exotic properties were extensively investigated in thermal equilibrium soon after their discovery but only recently have ultrafast techniques like femtosecond spectroscopy become available to study their out-of-equilibrium behaviour on the time-scale of atomic motion. By studying their behaviour on this time-scale a more in-depth understanding of their macroscopic properties can be gained. However, to do investigations on the atomic time-scale and simultaneously directly observe the evolution of the atomic arrangements is another challenge. One approach is through the previously mentioned technique of femtosecond pump-probe spectroscopy but converting the usual ultrashort optical probing source to an ultrashort electron or x-ray source that can diffract off the sample and reveal structural detail on the atomic level. Here, the femto-to-picosecond out-of-equilibrium behaviour upon photo-excitation in 4Hb-TaSe2 is investigated using an ultrashort electron probe source. Two variations of using an electron probe source are used: conventional scanning Femtosecond Electron Diffraction (FED) and a new approach namely Femtosecond Streaked Electron Diffraction (FSED). The more established FED technique, based on femtosecond pumpprobe spectroscopy, is used as the major investigating tool while the FSED technique, based on ultrafast streak camera technology, is an attempt at broadening the scope of available techniques to study structural dynamics in crystalline material on the subpicosecond time-scale. With these two techniques, the structural dynamics during the phase transition from the commensurate- to incommensurate-CDW phase in 4Hb-TaSe2 is observed through diffraction patterns with a temporal resolution of under 500 fs. The study reveals strong coupling between the electronic and lattice systems of the material and several time-constants of under and above a picosecond are extracted from the data. Using these time-constants, the structural evolution during the phase transition is better understood and with the newly gained knowledge, a model of all the processes involved after photo-excitation is proposed.
AFRIKAANSE OPSOMMING: In hierdie tesis word die strukturele dinamika van die lading-digtheid-golf (LDG) materiaal 4Hb-TaSe2 ondersoek op die tydskaal van atomiese bewegings en gelyktydig op die ruimtelikeskaal van atomiese dimensies. LDG materie is al van belang sedert hul ontdekking in die 1970’s as gevolg van hul merkwaardige nie-lineêre en anisotrope elektriese eienskappe, reuse diëlektriese konstantes, ongewone elastiese eienskappe en ryk dinamiese gedrag. Sommige van hierdie eksotiese eienskappe is omvattend ondersoek in termiese ewewig kort na hul ontdekking, maar eers onlangs is dit moontlik deur middle van ultravinnige tegnieke soos femtosekonde spektroskopie om hulle uit-ewewigs gedrag te bestudeer op die tydskaal van atomiese beweging. Deur die gedrag op hierdie tydskaal te bestudeer kan ’n meer insiggewende begrip van hul makroskopiese eienskappe verkry word. Om ondersoeke in te stel op die atomiese tydskaal en gelyktydig direk die evolusie van die atoom posisie te waarneem is egter ’n moeilike taak. Een benadering is deur middle van femtosekonde “pump-probe” spektroskopie maar dan die gewone optiese “probe” puls om te skakel na ’n electron of x-straal puls wat van die materiaal kan diffrak en dus strukturele inligting op die atomiese vlak kan onthul. Hier word die femto-tot-pico sekonde uit-ewewig gedrag in 4Hb-TaSe2 ondersoek met behulp van elektron pulse. Twee variasies van die gebruik van ’n elektron bron word gebruik: konvensionele “Femtosecond Electron Diffraction” (FED) en ’n nuwe benadering, naamlik, “Femtosecond Streaked Electron Diffraction” (FSED). Die meer gevestigde FED tegniek, wat gebaseer is op femtosekonde “pump-probe” spektroskopie, word gebruik as die hoof ondersoek metode terwyl die FSED tegniek, wat gebaseer is op die ultra vinnige “streak camera” tegnologie, ’n poging is om beskikbare tegnieke uit te brei wat gebruik kan word om strukturele dinamika in materie te bestudeer op die sub-picosekonde tydskaal. Met behulp van hierdie twee tegnieke, word die strukturele dinamika tydens die fase oorgang van die ooreenkomstige tot nie-ooreenkomstige LDG fase in 4Hb-TaSe2 deur diffraksie patrone met ’n tydresolusie van minder as 500 fs waargeneem. Die studie toon ’n sterk korrelasie tussen die elektroniese sisteem en kristalrooster. Verskeie tydkonstantes van onder en bo ’n picosekonde kon ook uit die data onttrek word en gebruik word om die strukturele veranderinge beter te verstaan. Hierdie nuwe kennis het ons in staat gestel om ’n model van al die betrokke prosesse voor te stel.
Miclea, Corneliu Florin. "Investigation of superconducting order parameters in heavy-fermion and low-dimensional metallic systems under pressure." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2006. http://nbn-resolving.de/urn:nbn:de:swb:14-1153315149468-90260.
Повний текст джерелаNichols, John A. "The development and implementation of electromechanical devices to study the physical properties of Sr2IrO4 and TaS3." UKnowledge, 2012. http://uknowledge.uky.edu/physastron_etds/3.
Повний текст джерелаZhang, Hao. "THE DEVELOPMENT AND IMPLEMENTATION OF SYSTEMS TO STUDY THE PHYSICAL PROPERITES OF TANTALUM TRISULFIDE AND SMALL-MOLECULE ORGANIC SEMICONDUCTORS." UKnowledge, 2015. http://uknowledge.uky.edu/physastron_etds/26.
Повний текст джерелаRitschel, Tobias. "Electronic self-organization in layered transition metal dichalcogenides." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-188265.
Повний текст джерелаKalinowski, Lech Stanisław. "Niskotemperaturowe badania własności fizycznych oraz wpływ domieszek na stan podstawowy Ce3Ru4Sn13 z silnymi korelacjami elektronowymi." Doctoral thesis, Katowice: Uniwersytet Śląski, 2017. http://hdl.handle.net/20.500.12128/5840.
Повний текст джерелаLeroux, Maxime. "Supraconductivité, Onde de Densité de Charge et Phonons Mous dans les dichalcogénures 2H-NbSe2 et 2H-NbS2, et le composé intermétallique Lu5Ir4Si10." Thesis, Grenoble, 2012. http://www.theses.fr/2012GRENY069/document.
Повний текст джерелаThis thesis presents an experimental study of the interaction between superconductivity and a charge density wave (CDW). In the standard theory, the critical temperature of a superconductor is principally enhanced by two parameters: a large density of states at the Fermi level (nF) and a strong electron-phonon coupling. However, a strong electron-phonon coupling also favors the appearance of a CDW, which reduces nF and therefore competes with superconductivity.Our strategy was to study two compounds in which superconductivity and CDW coexist, and in which the CDW can be suppressed through an external parameter: pressure or substitution. The first compound is 2H-NbSe2, it presents a CDW below 33 K at ambient pressure. This CDW coexists with superconductivity below 7 K. Under pressure, the CDW disappears above 4.6 GPa, meanwhile the critical temperature slowly changes. The CDW also disappears when replacing selenium by sulfur: 2H-NbS2 is a superconductor without CDW (Tc=6 K), it can therefore serve as a “test compound” for a comparative study. The second compound is Lu5Ir4Si10, it presents a CDW below 77 K at ambient pressure. Under pressure, this CDW disappears above 2 GPa, meanwhile the critical temperature abruptly jumps from 4 to 9 K.For this study, I used three experimental techniques: inelastic x-ray scattering at low temperature (300-2 K) and under pressure (0-16 GPa) to measure the dispersion of phonons, a tunnel diode oscillator to measure the temperature dependence of the magnetic penetration depth, and Hall microprobes to measure the first and second critical fields. In the first part, I present the temperature dependence of the phonon dispersion in 2H-NbS2. We observe a soft phonon that always remains at positive energies, even extrapolated to zero temperature. Thus, this compound is on the verge of CDW instability. It is also relatively unique, since we show anharmonicity is the only effect that prevents the complete softening of the phonons.Then I present the temperature and pressure dependence of the phonon dispersion in 2H-NbSe2. These experiments show that a soft phonon persists up to 16 GPa, even if the ground state is not a CDW. The temperature dependence of this soft phonon is then similar to that of 2H-NbS2. In both compounds, these soft modes seem to be related to the strength and anisotropy of the electron-phonon coupling. We suggest this is a fundamental element to explain their superconducting properties.In the second part, I measure the anisotropy and temperature dependence of the magnetic penetration depth in the superconducting state of 2H-NbS2 and Lu5Ir4Si10. The temperature dependence of the superfluid density in 2H-NbS2 confirms the presence of a reduced superconducting gap. Its amplitude is very similar to the one measured in 2H-NbSe2. The soft modes and the reduced gap being present in both 2H-NbSe2 and 2H-NbS2, we prove experimentally that the enhancement of superconductivity is related to the soft modes rather than to the nature of the ground state (CDW or metal). We suggest this enhancement is due the anisotropy of the electron-phonon coupling.However, this effect is not general to all compounds where superconductivity and CDW coexist. The superconducting properties of Lu5Ir4Si10 are indeed well fitted by the BCS model in the weak coupling limit. This may be related to the characteristics of the CDW: the presence of hysteresis shows that the CDW transition is first order. In addition, under pressure and at low temperature, x-ray diffraction measurements indicate that the CDW is multiple: aside from the periodicity of 1/7, we observe a second periodicity of 1/20
Miclea, Corneliu Florin. "Investigation of superconducting order parameters in heavy fermion and low dimensional metallic systems under pressure." Doctoral thesis, Göttingen Cuvillier, 2005. http://d-nb.info/990426440/04.
Повний текст джерелаKaddour, Wafa. "Coexistence Onde de Densité de Charge / Supraconductivité dans TTF[Ni(dmit)2]2." Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-00881509.
Повний текст джерелаDuverger-Nédellec, Elen. "Transitions vers des états électroniques complexes et des structures super périodiques dans les bronzes mono phosphates de tungstènes." Thesis, Normandie, 2017. http://www.theses.fr/2017NORMC239/document.
Повний текст джерелаConductive materials with low electronic dimensionality can present some transitions toward complex electronic states as superconductivity, Spin Density Waves (SDW) and Charge Density Waves (CDW). The coexistence of several of these instabilities in the same material leads to bustling investigations on new quasi-bidimensional conductors. In this thesis, we chose to study the MonoPhosphate Tungsten Bronzes with pentagonal channels family (MPTBp), of chemical formula (PO2)4(WO3)2m ; one of the main interests of this family is the possibility to directly control the compound’s dimensionality and its carriers density by varying m value (2 ≤ m ≤ 14). In the literature, it’s been shown that some MPTBp members (m=4, 5, 6) present successive CDW states whereas others (m=10) show ferroelectric-type orders. The aim of this thesis is thus to bring into light the effect of the material’s dimensionality on the appearance and the stability of these electronic states in the MPTBp family. In this way, transport measurements, X-Rays diffraction studies of the commensurate and incommensurate modulated structures below and above each transition and inelastic scattering measurements were done on several members with even value of m. In this work we reveal the existence of a CDW state for the m=2, 4, 6, 8 and 10 members, characterized by the formation of tungsten clusters in some areas of the crystal. For the m=8 and 10 members, the CDW is accompanied by a gradual installation of an anti-ferroelectric-like ordering of the tungsten atoms displacements. A CDW depinning phenomenon was observed for the quasi-unidimensional m=2 member, which has never been reported before in the MPTBp family. A strong electron-phonon coupling was evidenced for the high terms of the family (m ≥ 8) by structural analysis, first order resistive transitions observation and by X-Rays inelastic scattering measurements. For these high terms, an order-disorder transition must be considered
Federico, Mazza. "First Principle Calculations & Inelastic Neutron Scattering on the Single-Crystalline Superconductor LaPt2Si2." Thesis, KTH, Materialvetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-278071.
Повний текст джерелаDenna rapport presenterar en omfattande studie av enkristalls LaPt2Si2 i vilken supraledning och en laddningsdensitetsvåg (CDW) samexisterar. Användandet av DFT-modellering och neutronspridning har varit de huvudsakliga undersökningsmetoderna, för att bestämma alla karakteristiska drag hos det undersökta provet. Från resultaten kan observeras att den inneslutna Fermiytan är den huvudsakliga bidragaren till CDW-vågvektorn~qCDW = (1/3, 0, 0). Vidare visar den närvarande fonontillståndsdensiteten två typiska energinivåer, med mjuka lägen i Pt3-Pt4-skiktet, som stämmer överens med närvaron av en CDW. Den supraledande temperaturen har uppskattats till Tc = 1.6 K. Experimentella data från det inelastiska instrumentet HRC vid J-PARCs neutronkälla stämmer väl överens med teoretiska simuleringar, som visar samma energinivåer för polarisationsfononlägena (från 4 till 18 meV och från 32 till 42 meV).
Butaud, Patrick. "Etude par résonance magnétique nucléaire des ondes de densité de charge dans les conducteurs quasi-unidimensionnels inorganiques." Grenoble 1, 1987. http://www.theses.fr/1987GRE10018.
Повний текст джерелаBritel, Mohamed Reda. "Etude des propriétés élastiques du système unidimensionnel à onde de densité de charge (TaSe4)2I." Université Joseph Fourier (Grenoble), 1994. http://www.theses.fr/1994GRE10087.
Повний текст джерелаGonzalez, Vallejo Isabel. "Study of the structural dynamics of phase transitions using time resolved electron and X-ray diffraction." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS496.
Повний текст джерелаThe application of an external perturbation in certain materials (such as temperature, pressure or light) often gives rise to the emergence of new macroscopic properties with their origin at the atomic level. Therefore, a detailed study of the atomic dynamics becomes essential to the understanding of processes such as chemical transformations or phase transitions. In the particular case of structural phase transitions, the symmetry of the crystal undergoes a transformation between two different states at a given critical value. The typical time scales of the structural dynamics occur on the order of few hundreds of femtoseconds to several picoseconds. The development of femtosecond laser pulses has enabled scientists to access the required time scales to explore the ultrafast dynamics of the lattice structure in the relevant time scales. More precisely, time-resolved diffraction has proven to be an ideal technique to track and unveil the out-of-equilibrium pathways followed by the lattice after a short laser pulse.This thesis presents experimental studies performed by time-resolved electron and X-ray diffraction techniques on two different structural phase transitions. In a first part, we demonstrate the capabilities of the ultrafast electron diffraction (UED) experimental setup developed at Laboratoire d’Optique Apliquée. Our UED experimental results performed on high quality single crystal samples are presented along with a quantitative study of the implications of dynamical diffraction effects in UED experiments. In a second part, we present a set of pump-probe electron diffraction experiments performed on GdTe₃, a compound belonging to the rare-earth Tritellurides family which presents a charge density wave state. The arrival of an optical excitation triggers the phase transition non-thermally with the out-of-equilibrium relaxation dynamics of the charge density wave state characterized by slowing down that increases with incident fluence as well as with initial sample temperature. These results shed more light on current controversial interpretations involving the emergence of photoinduced topological defects. In a third part, we present time resolved X-ray diffraction experiments performed at CRISTAL beamline at SOLEIL synchrotron. In this case we have studied the A15 compound Nb₃Sn, which displays a displacive phase transition evolving from cubic to tetragonal symmetry at thermal equilibrium. Our pump-probe results present evidence of a different lattice response with respect to the thermal equilibrium transition, encouragingf uture investigations on the dynamics of this material
Chapeau-Blondeau, François. "Etude des mecanismes de polarisation electrique du polyethylene basse densite." Paris 6, 1987. http://www.theses.fr/1987PA066301.
Повний текст джерелаGuyot, Hervé. "Etude des transitions d'onde de densité de charge et des propriétés de transport des oxydes de molybdène [êta]-Mo4O11 et [gamma]-Mo4O11." Grenoble 1, 1986. http://www.theses.fr/1986GRE10122.
Повний текст джерелаRötger, Antonia. "Etude par magnétotransport de l'état d'onde de densité de charge dans les bronzes oxygénés quasi-bidimensionnels KMo6O17 et (PO2)4(WO3)2m." Grenoble 1, 1993. http://www.theses.fr/1993GRE10036.
Повний текст джерелаLorenzo-Diaz, José-Emilio. "Etude par diffusion de neutrons des transitions de phase dans les composés quasi-unidimensionnels (TaSe4)2I et (NbSe4)3I." Grenoble 1, 1992. http://www.theses.fr/1992GRE10184.
Повний текст джерелаLeriche, Raphaël. "Unconventional superconductivity in quasi-2D materials with strong spin-orbit coupling." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS577.
Повний текст джерелаThe realization of topological superconductors is one of the main current goals of condensed matter physics. It was indeed predicted that such systems should host Majorana fermions. These Majorana fermions possess both a non-Abelian statistics and, because of their topological origin, a certain robustness against local disorder, which makes them attractive for quantum computing applications. One approach likely to lead to topological superconductivity consists in considering superconducting systems with strong spin-orbit coupling and with broken inversion symmetry. It is in this framework that, during this thesis, I performed scanning tunneling microscopy and spectroscopy measurements on quasi-2D materials : (LaSe)1,14(NbSe2)2 and Sr2IrO4. I first studied the electronic properties of misfit compound LaNb2Se5, which is a parent of transition metal dichalcogenide 2H-NbSe2. (LaSe)1,14(NbSe2)2 is a heterostructure made out of alternations of NbSe2 bilayers with trigonal prismatic geometry and LaSe bilayers with rocksalt structure. (LaSe)1,14(NbSe2)2 is a potential candidate for topological superconductivity because of the presence of both a strong spin-orbit coupling and of broken inversion symmetry in NbSe2 planes. Here, I present spectroscopic results showing that the electronic structure of(LaSe)1,14(NbSe2)2 is very similar to the one of electron-doped monolayer NbSe2 with a shift of the chemical potential of 0,3 eV, priorly never reached. I could also demonstrate the quasi- 2D nature of (LaSe)1,14(NbSe2)2 and more particularly the presence of a strong Ising spinorbit coupling. Moreover, the observed weakness of superconductivity against non-magnetic disorder combined with quasiparticle interferences measurements allowed me to exhibit the unconventional nature of (LaSe)1,14(NbSe2)2 superconducting order parameter. This study opens the possibility to use misfit heterostructures such as (LaSe)1,14(NbSe2)2 to study thephysics of transition metal dichalcogenides in the 2D limit, for which many theoretical studies predict topological superconductivity. In this thesis, I also present a study on the effects of doping on the electronic properties of iridate compound Sr2IrO4. Sr2IrO4 is a spin-orbit induced Mott insulator. Because inversion symmetry is locally broken in Sr2IrO4, some theoretical predictions suggest that Sr2IrO4 should turn into a topological superconductor once doped. Here, I exhibit a nanometer-scaleinhomogeneous doping-driven Mott insulator to pseudo-metallic phase transition. This work further justifies the importance of using a local probe such as scanning tunnelling microscopy in order to complete results on Mott physics obtained by integrative methods like angle-resolved photoemission spectroscopy
Veuillen, Jean-Yves. "Etude par spectroscopie Mössbauer et de photoémission en rayonnement ultraviolet des bronzes bleus de molybdène A(0. 3)MoO3 (A = K, Rb)." Grenoble 1, 1986. http://www.theses.fr/1986GRE10146.
Повний текст джерелаBoujida, Mohamed. "Contribution à l'étude des propriétés de transport de quelques oxydes métalliques et supraconducteurs de basse dimensionnalité." Grenoble 1, 1988. http://www.theses.fr/1988GRE10157.
Повний текст джерелаBen, Salem Azzedine. "Synthese et caracterisation physique et structurale des conducteurs unidimensionnels de type fe : :(1+x)nb::(3-x)se::(10)." Nantes, 1987. http://www.theses.fr/1987NANT2018.
Повний текст джерелаKundu, Hemanta Kumar. "Probing charge-density waves and superconductivity in low-dimensional systems." Thesis, 2019. https://etd.iisc.ac.in/handle/2005/5042.
Повний текст джерелаChen, Yu-Yuan, and 陳裕元. "Physical Properties of Y5Ir4Si10 near Charge-Density-Wave Transitions." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/18323753624780141643.
Повний текст джерела國立東華大學
應用物理研究所
92
We present the results of electrical resistivity, Hall coefficient, magnetic susceptibility, specific heat, thermal conductivity, and thermoelectric power on the rare-earth-transition-metal compound Y5Ir4Si10 as a function of temperature. For all measured transport and thermodynamic properties, successive anomalies due to charge-density-wave (CDW) formation were observed. In contrast to the strong-coupled nature of the phase transitions found in that of its isostructural compounds R5Ir4Si10 (R = Dy - Lu), Y5Ir4Si10 could be described as a weak-coupled CDW system. Most interestingly, the complex temperature-dependent thermoelectric power and sign reversal of Hall coefficient in this material indicate a drastic modification of Fermi surface and a sudden change of the band structure, associated with the electron-hole asymmetry at the transitions.
Mahajan, Mehak. "Charge Density Wave-driven Carrier Transport in Layered Heterostructures." Thesis, 2022. https://etd.iisc.ac.in/handle/2005/5850.
Повний текст джерелаTsai, Huang-Ming, and 蔡煌銘. "Electronic Structures of RuO2, IrO2 Nanorods, Charge-density-wave K0.3MoO3 and High-density SiO2." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/84171405827453437893.
Повний текст джерела淡江大學
物理學系博士班
96
In this thesis, it is used the X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS) and scanning photoelectron microscopy (SPEM) to discuss the electronic and atomic structure of different condensed materials including RuO2 and IrO2 nanorods, quasi-one-dimension (1-D) blue bronze K0.3MoO3 and high-density SiO2 thin films. In RuO2 and IrO2 nanorods research, the results reveal that the hybridization between O 2p and metal t2g obitals is weaker in IrO2 than in RuO2. The tip-region enhancement of the SPEM intensity is greater for RuO2 than for IrO2, which suggests that RuO2 be a better material for field emission application. In 1-D blue bronze K0.3MoO3 material, the existence of the K+ ion has play an important role to connect the MoO3 octahedral structure and maintain the anisotropy structure in the charge-density-wave (CDW) transition. In the high density SiO2 thin films, we discovered that the different growth processes will cause the vary Si–O bonding, therefore we can control the dielectric parameter by changing the growth method.
Luo, Jhong-You, and 羅中佑. "X-Ray Studies of Quasi-One-dimensional Charge Density Wave Dynamics." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/36620573307114404700.
Повний текст джерелаLiao, Yin-Jiun, and 廖尹駿. "Resonant Soft X ray Scattering of Charge-density-wave Study in Chromium." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/43694837093473885960.
Повний текст джерела淡江大學
物理學系碩士班
97
In this study, we have demonstrated that CDW modulation in Cr can be probed using soft x-ray scattering. Because of the very weak signal from the satellite reflections caused by the formation of CDWs, it is difficult to undertake the detailed studies of CDWs with non-resonant x-ray scattering. However, with the help of resonant x-ray scattering, diffraction signals from weak satellite reflections could be largely enhanced. The wavelength λCDW was observed to have ~10a (a:lattice parameter of Cr) and Q_CDW≈(0.09 0 0) along [100] direction, and we obtained resonant enhancement of the signal near L2 and L3 edges. We studied the CDW peak at both of π and σ channels at T=77K and the temperature dependence between 70K and 300K at π channel.We also studied the temperature dependence of the Bragg peak.
Hsu, Fung-Hsueh, and 許芳雪. "Specific Heat Studies on the Charge-Density-Wave Transition of Lu5Ir4Si10 and Lu5Rh4Si10." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/48546944451382290399.
Повний текст джерела國立中山大學
物理學系研究所
89
Recently, the formation of charge density wave in 3D structure, Lu5Ir4Si10, had been observed in the X-ray diffraction experiment. At the same time, the transition in Lu5Ir4Si10 was thought to be first-order due to the spike-shaped anomaly in specific heat. The first-order transition usually accompanies with thermal hysteresis. In order to clarify this problem, we measure and analyze the specific heat result of Lu5Ir4Si10. As a matter of fact, we don’t observe the thermal hysteresis behavior within the resolution of our apparatus, and we think the formation of CDW in Lu5Ir4Si10 is strong interchain coupling. In addition, we also perform the resistivity, magnetic susceptibility and specific heat measurements under zero and external field on the isostructure component Lu5Rh4Si10 for comparison, which has also been thought to undergo a CDW transition. We indeed observe the thermal hysteresis behavior no matter on resistivity, susceptibility or on specific heat results, and this phenomenon doesn’t have magnetic effects. The thermal hysteresis features in Lu5Rh4Si10 are attributed to the presence of metastable states due to the pinning of the CDW phase to impurities, and we also discuss some possibilities about it. The specific heat measurement in our research is performed with an ac calorimetry, using chopped light as a heat source. The details of this technique are also discussed.