Screening effects in the electron-optical phonon interaction

We show that recently reported unusual hardening of optical phonons renormalized by the electron-phonon interaction is due to the neglect of screening effects. When the electron-ion interaction is properly screened optical phonons soften in three dimension. It is important that for short-wavelength optical phonons screening is static while for long-wavelength optical phonons screening is dynamic. In two-dimensional and one-dimensional cases due to crossing of the nonperturbed optical mode with gapless plasmons the spectrum of renormalized optical phonon-plasmon mode shows split momentum dependence.Comment: 7 page

Electron energy relaxation by phonons in the Kondo condensate

We have used normal metal-insulator-superconductor tunnel junctions as thermometers at sub-Kelvin temperatures to study the electron-phonon (e-p) interaction in thin Aluminum films doped with Manganese, as a function of Manganese concentration. Mn in Al is known to be a Kondo impurity with extremely high Kondo temperature $T_K \sim$ 500 K, thus our results probe the e-p coupling in the fully spin compensated, unitary limit. The temperature dependence of the e-p interaction is consistent with the existing theory for disordered metals, however full theory including the Kondo effect has not been worked out yet. The strength of the interaction decreases with increasing Manganese concentration, providing a means to improve sensitivity of detectors and efficiency of solid state coolers

Comment on "Giant Nernst Effect due to Fluctuating Cooper Pairs in Superconductors" by M.N. Serbyn, M.A. Skvortsov, A.A. Varlamov, and V. Galitski

In a recent Letter, Serbyn et al. [A] investigated thermomagnetic effects above the superconducting transition and generalized previous works for arbitrary magnetic fields and temperatures. While the results of [A] have been confirmed in [B], we have strong objections: (i) According to our results [C], the linear response calculation does not require any correction from the magnetization currents; (ii) The result of [A,B] is giant, because unlike the normal Fermi liquid, it is of zero order in the particle-hole asymmetry. Changing the interaction constant in the Cooper channel leads to ridiculously large results even for nonsuperconducting metals; (iii)Derived in [A] the Einstein-type relation for thermomagnetic coefficient contradicts to text-book results. [A] M.N. Serbyn, M.A. Skvortsov, A.A. Varlamov, V. Galitski, Phys. Rev. Lett. 102, 067001 (2009). [B] K. Michaeli and A.M. Finkel'stein, EPL 86, 27007 (2009). [C] A. Sergeev et al., Phys. Rev. B 77, 064501 (2008)

Coherent description of electrical and thermal impurity-and-phonon limited transport in simple metals

The electrical resistivity, thermoelectric power and electronic thermal conductivity of simple (isotropic) metals are studied in a uniform way. Starting from results of a variational solution of the Boltzmann equation, a generalized Matthiessen rule is used in order to superpose the inelastic (or not) electron-phonon and elastic electron-impurity scattering cross sections ("matrix elements"). The temperature dependence relative to these processes is given through simple functions and physical parameters over the usually investigated range of temperature for each transport coefficient. The coherence of such results is emphasized.Comment: 22 pages, 5 figures; to appear in International Journal of Modern Physics

Coulomb blockade in quantum dots under AC pumping

We study conductance through a quantum dot under Coulomb blockade conditions in the presence of an external periodic perturbation. The stationary state is determined by the balance between the heating of the dot electrons by the perturbation and cooling. We analyze two cooling mechanisms: electron exchange with the cold contacts and emission of phonons. Together with the usual linear Ohmic heating of the dot electrons we consider possible effects of dynamic localization. The combination of the abovementioned factors may result in a drastic change of the shape of the Coulomb blockade peak with respect to the usual equilibrium one.Comment: 12 pages, 8 figure