3,745 research outputs found
Coulomb drag at zero temperature
We show that the Coulomb drag effect exhibits saturation at small
temperatures, when calculated to the third order in the interlayer
interactions. The zero-temperature transresistance is inversely proportional to
the third power of the dimensionless sheet conductance. The effect is therefore
the strongest in low mobility samples. This behavior should be contrasted with
the conventional (second order) prediction that the transresistance scales as a
certain power of temperature and is almost mobility-independent. The result
demonstrates that the zero-temperature drag is not an unambiguous signature of
a strongly-coupled state in double-layer systems.Comment: 4 pages, 2 figure
Spin Torque Dynamics with Noise in Magnetic Nano-System
We investigate the role of equilibrium and nonequilibrium noise in the
magnetization dynamics on mono-domain ferromagnets. Starting from a microscopic
model we present a detailed derivation of the spin shot noise correlator. We
investigate the ramifications of the nonequilibrium noise on the spin torque
dynamics, both in the steady state precessional regime and the spin switching
regime. In the latter case we apply a generalized Fokker-Planck approach to
spin switching, which models the switching by an Arrhenius law with an
effective elevated temperature. We calculate the renormalization of the
effective temperature due to spin shot noise and show that the nonequilibrium
noise leads to the creation of cold and hot spot with respect to the noise
intensity.Comment: 10 pages, 7 figure
Spin-torque shot noise in magnetic tunnel junctions
Spin polarized current may transfer angular momentum to a ferromagnet,
resulting in a spin-torque phenomenon. At the same time the shot noise,
associated with the current, leads to a non-equilibrium stochastic force acting
on the ferromagnet. We derive stochastic version of Landau-Lifshitz-Gilbert
equation for a magnetization of a ''free'' ferromagnetic layer in contact with
a ''fixed'' ferromagnet. We solve the corresponding Fokker-Planck equation and
show that the non-equilibrium noise yields to a non-monotonous dependence of
the precession spectrum linewidth on the current.Comment: 5 pages, 2 figure
Dynamic response of one-dimensional interacting fermions
We evaluate the dynamic structure factor of interacting
one-dimensional spinless fermions with a nonlinear dispersion relation. The
combined effect of the nonlinear dispersion and of the interactions leads to
new universal features of . The sharp peak , characteristic for the Tomonaga-Luttinger model, broadens
up; for a fixed becomes finite at arbitrarily large .
The main spectral weight, however, is confined to a narrow frequency interval
of the width . At the boundaries of this interval the
structure factor exhibits power-law singularities with exponents depending on
the interaction strength and on the wave number
Full Counting Statistics for a Single-Electron Transistor, Non-equilibrium Effects at Intermediate Conductance
We evaluate the current distribution for a single-electron transistor with
intermediate strength tunnel conductance. Using the Schwinger-Keldysh approach
and the drone (Majorana) fermion representation we account for the
renormalization of system parameters. Nonequilibrium effects induce a lifetime
broadening of the charge-state levels, which suppress large current
fluctuations.Comment: 4 pages, 1 figur
Coulomb Blockade of Tunneling between Disordered Conductors
We determine the zero-bias anomaly of the conductance of tunnel junctions by
an approach unifying the conventional Coulomb blockade theory for ultrasmall
junctions with the diffusive anomalies in disordered conductors. Both,
electron-electron interactions within the electrodes and electron-hole
interactions between the electrodes are taken into account nonperturbatively.
Explicit results are given for one- and two-dimensional junctions, and the
crossover to ultrasmall junctions is discussed.Comment: 4 pages, 1 figure. Final version published in Phys. Rev. Let
Magneto-polarisability of mesoscopic rings
We calculate the average polarisability of two dimensional mesoscopic rings
in the presence of an Aharonov-Bohm flux. The screening is taken into account
self-consistently within a mean-field approximation. We investigate the effects
of statistical ensemble, finite frequency and disorder. We emphasize
geometrical effects which make the observation of field dependent
polarisability much more favourable on rings than on disks or spheres of
comparable radius. The ratio of the flux dependent to the flux independent part
is estimated for typical GaAs rings.Comment: pages, Revtex, 1 eps figur
- …