17 research outputs found
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
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
Disorder-Assisted Electron-Phonon Scattering and Cooling Pathways in Graphene
We predict that graphene is a unique system where disorder-assisted
scattering (supercollisions) dominates electron-lattice cooling over a wide
range of temperatures, up to room temperature. This is so because for
momentum-conserving electron-phonon scattering the energy transfer per
collision is severely constrained due to a small Fermi surface size. The
characteristic temperature dependence and power-law cooling dynamics
provide clear experimental signatures of this new cooling mechanism. The
cooling rate can be changed by orders of magnitude by varying the amount of
disorder which offers means for a variety of new applications that rely on
hot-carrier transport.Comment: 4 pgs, 2 fg
Effects of two dimensional plasmons on the tunneling density of states
We show that gapless plasmons lead to a universal
correction to the tunneling
density of states of a clean two dimensional Coulomb interacting electron gas.
We also discuss a counterpart of this effect in the "composite fermion metal"
which forms in the presence of a quantizing perpendicular magnetic field
corresponding to the half-filled Landau level. We argue that the latter
phenomenon might be relevant for deviations from a simple scaling observed by
A.Chang et al in the tunneling characteristics of Quantum Hall liquids.Comment: 12 pages, Latex, NORDITA repor
Quantum magneto-oscillations in a two-dimensional Fermi liquid
Quantum magneto-oscillations provide a powerfull tool for quantifying
Fermi-liquid parameters of metals. In particular, the quasiparticle effective
mass and spin susceptibility are extracted from the experiment using the
Lifshitz-Kosevich formula, derived under the assumption that the properties of
the system in a non-zero magnetic field are determined uniquely by the
zero-field Fermi-liquid state. This assumption is valid in 3D but, generally
speaking, erroneous in 2D where the Lifshitz-Kosevich formula may be applied
only if the oscillations are strongly damped by thermal smearing and disorder.
In this work, the effects of interactions and disorder on the amplitude of
magneto-oscillations in 2D are studied. It is found that the effective mass
diverges logarithmically with decreasing temperature signaling a deviation from
the Fermi-liquid behavior. It is also shown that the quasiparticle lifetime due
to inelastic interactions does not enter the oscillation amplitude, although
these interactions do renormalize the effective mass. This result provides a
generalization of the Fowler-Prange theorem formulated originally for the
electron-phonon interaction.Comment: 4 pages, 1 figur
Non Fermi liquid renormalization of the conductivity of fermions coupled to gauge fields
The method of the quantum kinetic equation is applied to the problem of renormalization of the conductivity of normal metals by gauge electronelectron interactions. It is shown that in the three-dimensional case the relativistic electromagnetic interaction (vector interaction of electrons with transverse photons) leads to an unusual temperature dependence, indicating a deviation from the Fermi liquid theory at low temperatures. In two dimensions such corrections are found to result from both the scalar (density-density or Coulomb) and the vector (current-current) gauge interactions. I. INTRODUCTION The renormalization of different electronic properties due to the electron-electron interactions constitutes one of the major premises of the Fermi liquid theory (FLT). Although there exists lots of results about renormalizations of such equilibrium thermal quantities as specific heat or Pauli magnetic susceptibility [1,2], there are very few statements concerning renormalizations of elect..