If the anisotrop y of the sup erconducting gap is ignored or w ashed out b y nonmagnetic impurit y scattering then theory simpli es and t c dep ends on 2 and a single function f whic h is similar to the phonondensit y of states f. Signatures of the electronphonon interaction, as they appear in conventional. Samin tajik, a bozidar mitrovic, a frank marsiglio b. Charge density wave cdw correlations are prevalent in all copperoxide superconductors. Electronphonon interaction an overview sciencedirect. Here, in order to further elucidate the influence of phonon dispersion, we have calculated the phonon modes in the entire brillouin zone of the naphthalene crystal. Recent studies point to the impact that the dispersion of both optical and acoustic phonons can have on the nonlocal electronphonon couplings in organic molecular semiconductors. Pdf 246 k pdf plus 270 k the effect of strong electronrattling phonon coupling on some superconducting properties. Anomalously suppressed thermal conduction by electron. Electronphonon coupling and superconductivityinduced. For weak coupling superconductors, which aredescribedby the famous bcs theory 1957,thereis a relation between the gap energyand the supercon. Electronphonon in general, electronion interaction is an important and ubiquitous process in solids, affecting almost all physical properties. Strong electronphonon coupling in yttrium under pressure. Electronphonon scattering and related electrical conductivity in noble and transition metals at high electron temperature y.
The detailed study of the phonon density of states from the surface atoms and central atoms shows a better understanding of the nontrivial size dependence of the heat transport in silicon nanowire. Angle resolved photoemission spectroscopy arpes and scanning tunneling microscopyspectroscopystms are two spectroscopic techniques which can detect the consequences of electronphonon coupling on a materials electronic structuredensity of. Abstract superconductivity in some metals at low temperature is known to arise from an electronphonon coupling mechanism. Jeffrey snyder1 department of materials science, california institute of technology, pasadena, ca 91125. The surprisingly weak electronacoustic phonon coupling stimulates us to query the reason behind.
The intrinsic limits to conductivity and mobility at. This lecture addresses the consequences of electronphonon coupling in both the normal and the superconducting state of metals. A positive negative gate voltage accumulates carriers at depletes. Polaronic behavior in a weakcoupling superconductor.
Electronphonon coupling in metallic solids from density. Purely timeresolved studies typically cannot separate these two contributions and have consistently neglected lateral heat flow 25, 27, which becomes particularly important when. The electronphonon coupling constant is gkk0 wkk0 e q v u u u u t n 2m. Thermal transport properties of gan with biaxial strain. Majumdar and reddy3 first introduced the twotemperature model to explain the role of eph coupling in thermal conductance of a metalnonmetal interface. Unlike bcs superconductors, where the superconducting gap has an swave symmetry, early experiments on htsc indicated singlet cooper pairing with a d. Electronphonon coupling epc also provides in a fundamental way an attractive electronelectron interaction, which is always present and, in many metals, is the origin of the electron pairing underlying the macroscopic quantum phenomenon of superconductivity.
Role of electronphonon coupling in thermal conductance of. Hoffman,3 xucun ma,1, and qikun xue1,2, 1state key laboratory for surface physics, institute of physics, chinese academy of sciences, beijing 100190, china. Imaging the electronboson coupling in superconducting. No super conductivity at any temperature even approaching1kresults with. Electronphonon coupling, superconductivity and nontrivial. Electron boson coupling plays a key rolein superconductivity for many systems. Without with the spinorbit coupling soc effect the super conducting transition temperature of t c is derived to be 1. How the electronphonon coupling mechanism work in metal.
There are two different relaxation processes that decrease the efficiency of light conversion in a solar system. This lecture addresses the consequences of electronphonon coupling in both the. Lefkidis university of kaiserslautern and research center optimas, box 3049, 67653 kaiserslautern, germany targoviste, 29 august 2011. T, signifying that holetype carriers dominate the thermoelectric transport fig. The effect of the electronphonon coupling on the thermal. Large thermoelectric power factor from crystal symmetry. However, in copperbased highcritical temperature tc superconductors, its relation to superconductivity remains controversial despite strong spectroscopic fingerprints. Typically, at temperatures greater than of the debye temperature, the lifetimes of phonons that dominate.
Intertwined growth of super conductivity and epc tuned by. Superconductivity with strong electronphonon coupling in. Hence manipulation of the electronphonon coupling is an important issue to realize graphenebased electronicandspintronicdevices4andtocreatenewstrongly correlated electron phases. Effect of electronphonon coupling on the superconducting transition.
The reason for this is that the electron phonon coupling strength in all kno wn sup erconductors w as deemed to b e su. Under a compressive strain state, the decreases of lattice thermal conductivity are 19% and 23% for inplane and crossplane conditions, respectively, comparable with those under a free state. Tracking ultrafast hotelectron diffusion in space and. However, the decreases are small under the tensile strain state, because of the decreased electronphonon scattering rates and increased phonon. The phonon contribution to the thermal conductivity of a metal has a complex dependence on temperature, lattice anharmonicity, and the strength of electronphonon coupling.
Superconductivity rapid change of superconductivity and. Electronphonon coupling and the superconducting phase. Superconductivity and bcs theory introduction electronphonon interaction, cooper pairs bcs wave function, energy gap and quasiparticle states predictions of the bcs theory limits of the bcs gap equation. While cdws in conventional metals are driven by coupling between lattice vibrations and electrons, the role of the electron phonon coupling epc in cuprate cdws is strongly debated. Extreme electronphonon coupling in boronbased layered.
Although most of the features observed in the optical conductivity spectra can be explained by a large polaron model 14,15, there is still no consensus about. An effective attractive interaction between the electrons results from exchange of virtual phonons. Weak electron phonon coupling contributing to high. Influence of electronphonon coupling strength on signatures of even and oddfrequency superconductivity preprint pdf available december 2019 with 36 reads how we measure reads. We theoretically show that the thermal conductance associated with electronphonon coupling in a metal near a metalnonmetal interface can be estimated as h ep gk p, where g is the volumetric electronphonon coupling constant and k p is the phonon or lattice thermal conductivity of the metal. F ermiliquid theory of superconductivity to metals with strong electron phonon coupling. How to detect electronphonon coupling by arpes and stm in. Enhanced electron phonon coupling and its irrelevence to high tc superconductivity. Polaronic behavior in a weakcoupling superconductor adrian g. These results demonstrates strong electronphonon coupling in this system that can account for the observed range of tc. Pdf influence of electronphonon coupling strength on. Having shown that electronphonon coupling can be directly observed in the laalo 3 srtio 3 tunnel junctions, we now discuss its relation to superconductivity. Phonon spectrum and electronphonon coupling in zigzag. Electronphonon interaction in a semiconductor is the main factor for relaxation of a transferred electron.
Lattice distortions and vibrations can couple with electronic structure to limit electronic carrier mobility, and turning this around, electronphonon coupling can limit lattice thermal conductivity by scattering of phonons. Impact of phonon dispersion on nonlocal electronphonon. Stanford institute for materials and energy sciences. The electron relaxation and thermalization of the two subsystems are a direct result of an interplay between electronphonon coupling and hotelectron diffusion. Coupling between electrons and phonons lattice vibrations drives the formation of the electron pairs responsible for conventional superconductivity. Superconductivity with strong electronphonon coupling in noncentrosymmetric w3al2c. In metals, where the relaxation processes depend on both electrons and phonons, all thermodynamic and transport. Electronoptical phonon coupling in superconductors. Survey of ab initio phonon thermal transport sciencedirect. These results indicate that the electron phonon coupling is of moderate strength and is easily capable of supporting the observed superconductivity. Effect of electronphonon coupling on thermal transport.
In order to improve the accuracy of the model, which is critical in the study of micro and nanoscale heat transfer and interface heat transfer 4,5, g. We investigate the role of the optical phonons in superconductivity in the case of compounds with different atomic massesm k. In the weak coupling case, z 1, c 0, and fd, the super conducting gap. Landau institute for theoretical physics ras electrical conductivity of noble and transition metals due to the electronphonon collisions is calculated in twotemperature state. Imaging the electronboson coupling in superconducting fese films using a scanning tunneling microscope canli song,1,2,3 yilin wang,1 yeping jiang,1,2 zhi li,1 lili wang,1 ke he,1 xi chen,2 jennifer e.
Ytterbiumdriven strong enhancement of electronphonon. In fact, several methods have been proposed to modify the electronphonon coupling. Pdf evidence for ubiquitous strong electronphonon coupling in. Thermoelectric signatures of the electronphonon fluid in ptsn. The same formalism can be extended to the normal state by setting f 0. Rapid change of superconductivity and electronphonon coupling through critical doping in bi2212 y. These results point towards a key role played by the coupling of electrons to optical phonon modes, thus forming large polarons 14. The electronphonon coupling in doped babio3 has been investigated theoretically by several methods. Lecture notes on superconductivity a work in progress.
In order to simplify the notation,we shall make the convention that all phonon wavevectors must be mapped into the. Upon cooling, s exhibits a sign reversal at 50 k followed by a large, negative phonondrag peak centred around t pd 14 k, which is consistent with the literature. Abstract in this thesis we investigate the electronic and vibrational properties of several transitionmetal dichalcogenide materials through. They can be viewed as bosonic particles which propagate through the crystal and interact with electrons. Electronphonon interaction in conventional and unconventional. Strong confir mation of the importance of electronphonon.
Like landaus f ermiliquid theory it lives on the border line between microscopic theories and. Influence of electron phonon coupling strength on signatures of even and oddfrequency superconductivity preprint pdf available december 2019 with 36 reads how we measure reads. Electronphonon interaction and superconductivity in bair2p2. Radiative processes coulomb interactions among free.
Firstprinciples study of charge density waves, electron. The revolutionary discovery of hightemperature superconductors in 1986 is still shaking the condensed matterphysics, solidstatechemistry. Electronphonon coupling and properties of doped babio. The electronphonon coupling constant for fese as obtained in linear response is 0. This places srtio3, a host material for a variety of. We measured the gatevoltage dependence of the phononassisted tunneling in a device for which we previously determined the superconducting phase diagram 15. We will first give a brief discussion of the electronphonon interactions as applied to superconductivity theory from.
Request pdf electronphonon coupling, superconductivity and nontrivial band topology in nbn polytypes in this paper, we investigate the electronic band structure, lattice dynamics and electron. The effect of strong electronrattling phonon coupling on. Neglecting the electronphonon coupling leads to overestimation of the thermal transport for ultrathin sinws. Pickett, uc davis summer school on novel superconductivity, august 2009. This is of interest independent of super conductivity to be discussed below, as the electronphonon coupling affects many other properties of materials, such as the conductivity. Topological metal of nabi with ultralow lattice thermal. Weak electronphonon coupling contributing to high thermoelectric performance in ntype pbse heng wang, yanzhong pei1, aaron d. Coupling between electrons and phonons lattice vibrations drives the formation of the electron pairs responsible for conventional superconductivity 1. Electronphonon interaction that normally plays negligible role in lattice thermal conduction of crystalline materials is found to dominantly scatter phonons and limit thermal conduction in a charge. The phonon density of states dos, g, and electronphonon spectral function, 2f, are given in fig.
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