Pdf electronphonon interaction and superconductivity in. The lowestorder process involving the electronphonon interaction is the scattering of a single electron by a simultaneous creation or annihilation of a single phonon, as diagrammatically shown in fig. The nobel prize in physics 1972 was awarded jointly to john bardeen, leon neil cooper and john robert schrieffer for their jointly developed theory of superconductivity, usually called the bcstheory. Electronphonon interaction and superconductivity in bair2p2. Electronphonon interaction in a superconductor with kondo. Strong electronphonon interaction retarding phonon.
The interaction between an electron and a lattice vibration can be treated as a. Electronphonon interactions and superconductivity nasaads. The electron electron and electron impurity potentials are respectively equal to where zion is the valence of an atom of the host lattice, zimp that of the impurity atom, and r is the equilibrium impuri ty position. However, in the list of graphenes many remarkable properties 3,4,5,6, superconductivity is notably absent. Pdf signature of electronphonon interaction in high. Electronphonon interaction in a semiconductor is the main factor for relaxation of a transferred electron.
The probability for the scattering process is called the electronphonon vertex g. By extracting the superconducting properties, phonon density of states, and electronphonon coupling function from these measurements, we. On the other hand, the phonon at around 620 cm1, which is theoretically predicted to interact most strongly with the electronic system, showed systematic decrease of the thermal broadening upon reducing the carrier concentration, which is interpreted as weakening of the electron phonon interaction. We will first give a brief discussion of the electronphonon interactions as applied to superconductivity theory from 1950 to. In a superconductor with magnetic impurities, kondo scattering results in the formation of localized states inside the superconducting gap. Pdf electronphonon interaction in high temperature. The revolutionary discovery of hightemperature superconductors in 1986 is still shaking the condensed matterphysics, solidstatechemistry. The problem of conventional, lowtemperature superconductivity has been regarded as solved since the seminal work of bardeen, cooper, and schrieffer bcs more than 50 years ago. Role of the electronphonon interaction in the strongly.
Electronphonon coupling in high temperature superconductors. High temperature superconductivity, along with more recent developments with other newly discovered superconducting materials, have led to a superconducting renaissance over the past 20 years. Effect of electronphonon coupling on the superconducting transition. Signature of electron phonon interaction in high temperature superconductorssignature of electron phonon interaction in high temperature superconductors vinod ashokan,1,a. Section 4 is devoted to phononmediated super conductivity. Physical properties and superconductivity of heusler. Electronphonon interaction an overview sciencedirect. Electronic band structure, electronphonon interaction. Then, we will focus on the elph interaction, analyzing in its intraband and inter. By integrating the eliashberg spectral function, the value of average electron. We discuss the possible enhancement of superconducting transition temperature by local inhomogeneity introduced by doping. We investigate the complete phonon dispersion, the phonon induced electronic charge response and the corresponding selfconsistent change of the crystal potential an electron feels as a direct measure of the electron phonon interaction in the hightemperature superconductors within a microscopic model in the framework of linear response theory. These results indicate that the electron phonon coupling is of moderate strength and is easily capable of supporting the observed superconductivity. Electron phonon coupling epc in cuprate and ironbased superconducting systems.
Electronphonon interaction and superconductivity in metallic molecular hydrogen. Phononmediated superconductivity in graphene by lithium. Introduction electron phonon eph interaction at conducting surfaces together with its dimensionality are of great importance both at fundamental and technological levels. Electronphonon interaction using wannier functions. However, the theory does not allow accurate predictions of some of the most fundamental properties of a superconductor. Graphene 1 is the physical realization of many fundamental concepts and phenomena in solidstate physics 2. Phonons, electronic charge response and electronphonon interaction in the high. Phonon, electronphonon interaction and superconductivity. Electronphonon interactions a superconductiv john bar our present understanding of superconductivity has arisen from a close interplay of theory and experiment.
An analysis of electron phonon interaction properties reveals that acoustic phonon branches are more involved in the process of scattering of electrons than optical phonon branches. However, electron phonon mediated superconductivity is still not well understood, especially in lower dimensional systems. It would have been very difficult to have arrived at the theory by purely deductive reasoning from the basic equations of quantum mechanics. We study the influence of the intrinsic electron phonon interaction epi on the phonon transport of superconducting hydrogen sulfide at high pressures, and its variation. First a derivation of the effective attractive interaction among electrons mediated by phonon. Electron phonon interaction in high temperature superconductors article pdf available in iranian journal of physics research 63 september 2006 with 89 reads how we measure reads. There are two different relaxation processes that decrease the efficiency of light conversion in a solar system. The interaction between electrons and phonons is central to many phenomena, including electrical and thermal transport and superconductivity. The polaron concept was first proposed by lev landau in 1933 to describe an electron moving in a dielectric crystal where the atoms move from their equilibrium positions to effectively screen the charge of an electron, known as a phonon cloud. Phonon mediated attractive interaction and the cooper pairs.
The electronphonon interaction of lowdimensional and. Strong confirmation of the importance of electronphonon interactions in superconductivity came from the independent experimental discovery of the isotope effect. D billington et al fermi surface properties of ab3 a y,20 supercond. Role of the electron phonon interaction in the strongly correlated cuprate superconductors. In conventional superconductors, this attraction is due to the electron phonon interaction. Electronphonon interaction in conventional and unconventional. We have displayed the calculated eliashberg spectral function and the average electronphonon coupling parameter together in fig.
We show that inelastic electronic transitions involving quasiparticle scattering into and out of the localized states may result in significant changes in the non equilibrium properties of the superconductor. The phonon acts as the matchmaker bringing the electrons together into pairs. Earlier, interac tions between electrons and phonons the quanta of the lattice vibrations were taken into account for scattering and resistance. Realistic representation of quantum interactions between electrons and phonons is crucial to uncovering the fundamental origin of superconductivity and predicting superconductors with a high transition temperature t c. Recently the electron phonon eph interaction has been the focus of intense research efforts in the physics of hightemperature superconductivity and nanoscale transport. A strong electron phonon interaction results in a high scattering level of electrons by the thermal vibrations and hence comparatively poor. In a previous work, we investigated the possibility of a superconducting phase transition in molecular metallic hydrogen cmca within dft framework18 and on the basis of densityfunctional theory extended to the superconducting state,19 properly accounting for electron phonon elph and electron electron interaction. Abstract superconductivity in some metals at low temperature is known to arise from an electronphonon coupling mechanism. Our electron phonon interaction calculations suggest that the mechanism for superconductivity is heavily governed by interactions of electrons with acoustic phonon modes and lowfrequency optical phonon modes, which strongly modulate. A number of theoretical works have also proposed the exotic p wave superconductivity in this family 18,33,34,35,36,37,38. The electron phonon interaction in metals nicolas bock october 27, 2003 advisor. It emerges from this study that present model of electron phonon interactions responsibly puts its signatures in high temperature superconductivity and successfully explains the experimental observations of thermal conductivity strengthening the idea of electron phonon coupling responsible for high temperature superconductivity. Hamiltonian the basic interaction hamiltonian is hh h h pe ei 12 pq qq q haa 2 11 2 22 i e iijij p he mr ei i ei i j iij hvr vrr taylor series expansion for the displacements the electron.
Electronphonon interaction and superconductivity in metals. Electronphonon coupling epc in cuprate and ironbased superconducting systems. Phonon and electron phonon interaction properties of liga 2 rh are weakly influenced by the inclusion of spin orbit coupling. If it were possible to find a way to induce superconductivity, it could improve the performance and enable more efficient. The cooper pair state is responsible for superconductivity, as described in the bcs theory developed by john bardeen, leon cooper, and john schrieffer for which they shared the 1972 nobel prize. We will first give a brief discussion of the electronphonon interactions as applied to superconductivity theory from 1950 to 1957, when the pairing theory. One of the main goals of this work is to analyze the strength of electronphonon interaction in y2c in order to find the origin of superconductivity in this superconductor.
Electron phonon superconductivity in yin 3 to cite this article. Concepts of fermi liquid theory and instability of the normal state. Pdf evidence for ubiquitous strong electronphonon coupling in. A polaron is a quasiparticle used in condensed matter physics to understand the interactions between electrons and atoms in a solid material. Electronphonon interactions and superconductivity science.
Pdf coupling between electrons and phonons lattice vibrations drives. Electronphonon interaction and superconductivity in. Related content firstprinciples study of the electronic, vibrational, electron phonon interaction. However, the theory does not allow accurate predictions of some of the most fundamental properties of a superconductor, including the superconducting energy gap on the. Unlike bcs superconductors, where the superconducting gap has an swave symmetry, early experiments on htsc indicated singlet cooper pairing with a d. The electron phonon interaction and strongcoupling superconductors by douglas j. The probability for the scattering process is called the electronphonon. Electron phonon interactions and superconductivity. How the electronphonon coupling mechanism work in metal. Scalapino bardeen and schrieffer discuss details of the interactions of electrons and phonons in a given metal sought in deviations of observed properties from the original bcs predictions. Strong confir mation of the importance of electronphonon. Effects of the electronphonon interaction in hexagonal.
Dermot co ey a dissertation submitted to the faculty of the graduate school of the state. An effective attractive interaction between the electrons results from exchange of virtual phonons. Phonons, electronic charge response and electronphonon. The problem of conventional, lowtemperature superconductivity has been regarded as. While the 5,5 and 10,10 tubes are chosen to study the effect of curvature on the electron phonon interaction the 5,0 tube is chosen because it has the diameter 3. Electronphonon interaction and superconductivity in the. Pdf electronphonon interactions and superconductivity. Superconductivity and bcs theory introduction electron phonon interaction, cooper pairs bcs wave function, energy gap and quasiparticle states predictions of the bcs theory limits of the bcs gap equation. Electronphonon coupling and its implication for the. The first page of the pdf of this article appears above. A fairly sophisticated description of electronphonon superconductivity has existed since the early 1960s, following the work of eliashberg 1, nambu 2, morel and anderson 3, and schrieffer et al.
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