1,003 research outputs found
Weak localization effect on thermomagnetic phenomena
The quantum transport equation (QTE) is extended to study weak localization
(WL) effects on galvanomagnetic and thermomagnetic phenomena. QTE has many
advantages over the linear response method (LRM): (i) particle-hole asymmetry
which is necessary for the Hall effect is taken into account by the
nonequilibrium distribution function, while LRM requires expansion near the
Fermi surface, (ii) when calculating response to the temperature gradient, the
problem of WL correction to the heat current operator is avoided, (iii)
magnetic field is directly introduced to QTE, while the LRM deals with the
vector potential and and special attention should be paid to maintain gauge
invariance, e.g. when calculating the Nernst effect the heat current operator
should be modified to include the external magnetic field. We reproduce in a
very compact form known results for the conductivity, the Hall and the
thermoelectric effects and then we study our main problem, WL correction to the
Nernst coefficient (transverse thermopower).Comment: 20 pages 2 figure
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 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)
- …