Effect Of Electron-phonon Research Articles

Theory of Seebeck ratchet in a noncentrosymmetric electron-phonon coupled system

A thermoelectric effect of the noncentrosymmetric electron-phonon coupled system is proposed, in which a temperature difference between electrons and phonons, instead of a spatial temperature gradient, induces an electric current. This is a realization of Seebeck ratchet in solids with the asymmetric energy dispersion of electrons, and the dynamical phonons act as the fluctuation of the scalar potential and induce the dc current. Possible realizations of this mechanism are also discussed.

Study of electron-phonon coupling and its effect on electrical resistivity in HF systems

In this work, we report on theoretical study of the effect of electron-phonon (EP) interaction in THz frequency and temperature dependence of the electrical resistivity in heavy fermion (HF) systems. For this purpose, a model Hamiltonian is considered which consists of the Heisenberg type exchange interaction between localized moments and a tight binding model called the Kondo lattice model (KLM). The effect of EP coupling on electrical resistivity is presented by considering phonon interaction to bare f-electrons, band electrons and to the hybridization between band and f-electrons as a perturbed term. The phonon Hamiltonian in harmonic approximation is also included. The model Hamiltonian is solved by employing the mean-field theory (MFT) along with the Hubbard model of approximation. The temperature- and frequency-dependent electrical resistivity exhibits change in slopes at T[Formula: see text] as well as at T[Formula: see text]. The theoretical findings from the graphical analysis by varying the model parameters g[Formula: see text], g[Formula: see text] and g[Formula: see text] are compared to some of the experimental results in HF systems.

Third-harmonic generation in a double ring-shaped quantum dot under electron-phonon interaction

In this work, the effect of electron-phonon (e-p) interaction on third-harmonic generation (THG) in a GaAs double ring-shaped quantum dot is studied. To this end, we have analytically obtained the energy levels and wave functions without the interaction between electron and phonon. Then, we have used THG coefficient which is obtained by using compact-density-matrix approach and iterative method. Numerical obtained results reveal that the THG coefficient is obviously increased and the peak positions shift toward higher energies after considering the e-p interaction.

Effect of electron-phonon coupling on thermal transport across metal-nonmetal interface —A second look

The effect of electron-phonon (e-ph) coupling on thermal transport across metal-nonmetal interfaces is yet to be completely understood. In this paper, we use a series of molecular-dynamics (MD) simulations with e-ph coupling effect included by Langevin dynamics to calculate the thermal conductance at a model metal-nonmetal interface. It is found that while e-ph coupling can present additional thermal resistance on top of the phonon-phonon thermal resistance, it can also make the phonon-phonon thermal conductance larger than the pure phonon transport case. This is because the e-ph interaction can disturb the phonon subsystem and enhance the energy communication between different phonon modes inside the metal. This facilitates redistributing phonon energy into modes that can more easily transfer energy across the interfaces. Compared to the pure phonon thermal conduction, the total thermal conductance with e-ph coupling effect can become either smaller or larger depending on the coupling factor. This result helps clarify the role of e-ph coupling in thermal transport across metal-nonmetal interface.

Study of Low Temperature Specific Heat in La-Ba/Sr-CuO Superconductors

The low temperature specific heat of La 1.85 Ba 0.15 CuO 4 and La 1.8 Sr 0.2 CuO 4 superconductors has been investigated based on the free electron, layered electron gas model of quasi-two-dimensional (2D) layers of CuO 2 along the a-b plane. The interaction potential properly incorporates the effect of electron-electron, electron-phonon and electron-plasmon interactions. The lattice contribution to the specific heat is well estimated from the electron-phonon part of the interaction potential. The results on the behaviour of the specific heat (C) with temperature (T) for both systems are similar to those observed in previous experiments. It is noticed that the specific heat contribution from the Debye model is significant at low temperatures (5 K ≤ T ≤ T c ) while the Einstein model affords the specific heat at higher temperatures (T ≥ T c ). The estimated lattice specific heat, when subtracted from the experimental data, results in a finite value of the electronic specific heat coefficient (γ). Non-zero values of γ indicate the electronic origin intrinsic to these superconductors. A linear temperature dependence of ΔC (= C exp - C latt )/T in the range 20 K ≤ T ≤ 45 K is depicted. Furthermore, the density of states at the Fermi level is also estimated. The results derived are consistent with the reported data. The implications of the above analysis are discussed.

Effect of electron-phonon interaction on a one-dimensional correlated electron system.

The effect of an on-site electron-phonon (e-ph) interaction is studied within the framework of an extended Hubbard model in one dimension. We have eliminated the local phonon coordinates using a modified Lang-Firsov transformation and diagonalized the effective electronic Hamiltonian by a real space renormalization group technique to determine the transition from a charge density wave (CDW) state to a spin density wave (SDW) state. It turns out that the CDW phase is favored by the e-ph coupling with an appreciable band-narrowing effect. In the SDW phase the distortions produced at nearest neighbor sites due to the e-ph interaction become comparable to the on-site distortions while this retardation effect is negligible in the CDW phase. \textcopyright{} 1996 The American Physical Society.

Nonequilibrium Phonon Distributions in Metals

The effect of a nonequilibrium phonon distribution on some of the transport properties of metals is calculated in the presence of electric and thermal currents and a magnetic field. It is shown that the lattice heat current contains an additional term not found in the literature which is equal in magnitude to the terms usually retained, and that this term represents the contribution from the nonequilibrium part of the electron energy distribution. Thus, the heat current carried by the lattice in metals is dependent on the magnitude of the electron current. Further, the effect of electron phonon scattering caused by a nonequilibrium phonon distribution on the Ettingshausen and Ettingshausen-Nernst coefficients is shown to be insufficient to explain the anomalous behavior of these coefficients for metals.