459 research outputs found

### The Boltzmann--Langevin approach: A simple quantum-mechanical derivation

We present a simple quantum-mechanical derivation of correlation function of
Langevin sources in the semiclassical Boltzmann--Langevin equation. The
specific case of electron--phonon scattering is considered. It is shown that
the assumption of weak scattering leads to the Poisson nature of the scattering
fluxes.Comment: 4 pages, 1 figure, invited contribution to special issue in Physica E
on "Frontiers in quantum electronic transport - in memory of Markus
B\"uttiker

### Comment on "Universality of the 1/3 shot-noise suppression factor in nondegenerate diffusive conductors"

We argue that the nearly 1/3 suppression of shot noise in nondegenerate
diffusive contacts recently obtained by Gonzalez et al. (cond-mat/9803372) is
due to the specific choice of the energy-independent elastic scattering time.Comment: 2 pages, RevTex, no figure

### Electron-electron scattering and conductivity of long multimode channels

The electron-electron scattering increases the resistance of ballistic
many-mode channels whose width is smaller than their length. We show that this
increase saturates in the limit of infinitely long channels. Because the
mechanisms of angular relaxation of electrons in three and two dimensions are
different, the saturation value of the correction to the resistance is
temperature-independent in the case of three-dimensional channels and is
proportional to the temperature for two-dimensional ones. The spatial behavior
of electron distribution in the latter case is described by an unusual
characteristic length.Comment: 8 pages, 3 figure

### How an incorrect transition from finite to infinite 2D conductor may result in a false negative relaxation

We consider the relaxation of a uniform current in a planar 2D conductor with
account taken of electromagnetic retardation effects. If the 2D conductivity is
larger than the speed of light, the straightforward solution for an infinite
plane gives a negative relaxation rate. However if one starts from a conducting
cylinder of finite radius and then increases it to infinity, the relaxation
rate just tends to zero while remaining positive. We suggest that recent
unusual plasmon-dispersion curves obtained by V. A. Volkov and A. A.
Zabolotnykh [arXiv:1605.00430] result from the incorrect finite-to-infinite
transition.Comment: Typo in Eq. 5 correcte

### Frequency-dependent shot noise in long disordered SNS contacts

The shot noise in long diffusive SNS contacts is calculated using the
semiclassical approach. At low frequencies and for purely elastic scattering,
the voltage dependence of the noise is of the form S_I = (4\Delta + 2eV)/3R.
The electron-electron scattering suppresses the noise at small voltages
resulting in vanishing noise yet infinite dS_I/dV at V = 0. The distribution
function of electrons consists of a series of steps, and the frequency
dependence of noise exhibits peculiarities at \omega = neV, \omega = neV -
2\Delta, and \omega = 2\Delta - neV for integer n.Comment: 4 pages, 4 eps figure

### Nonlinear conductivity of diffusive normal-metal contacts

Metal microbridges with a high impurity content and shorter than the energy
relaxation length are considered. Their conductance is calculated with
allowance made for the Coulomb electron-electron interaction. It is shown that
nonequilibrium electrons in the microbridges gives rise to a nonlinear
current-voltage characteristic (published in Physics Letters A, 1994).Comment: 3 pages, 2 eps figure

### Electron-electron scattering and magnetoresistance of ballistic microcontacts

Using a semiclassical Boltzmann equation, we calculate corrections to the
Sharvin conductance of a wide 2DEG ballistic contact that result from an
electron--electron scattering in the leads. These corrections are dominated by
collisions of electrons with nearly opposite momenta that come from different
reservoirs. They are positive, increase with temperature, and are strongly
suppressed by a magnetic field. We argue that this suppression may be
responsible for an anomalous positive magnetoresistance observed in a recent
experiment.Comment: 10 pages, 8 figures, published versio

### Charge and spin current in a quasi-one-dimensional quantum wire with spin-orbit coupling

We show that Rashba spin-orbit coupling may result in an energy gap in the
spectrum of electrons in a two-mode quantum wire if a suitable confining
potential is chosen. This leads to a dip in the conductance and a spike in the
spin current at the corresponding position of the Fermi level. Therefore one
may control the charge and spin currents by means of electrostatic gates
without using magnetic field or magnetic materials.Comment: 5 pages, 5 figures, published versio

### Non-universal shot noise in quasiequilibrium spin valves

We show that the breakdown of the Wiedemann-Franz law due to
electron--electron scattering in diffusive spin valves may result in a strong
suppression of the Fano factor that describes the ratio between shot noise and
average current. In the parallel configuration of magnetizations, we find the
universal value $\sqrt{3}/4$ in the absence of a normal-metal spacer layer, but
including the spacer leads to a non-monotonous suppression of this value before
reaching back to the universal value for large spacer lengths. On the other
hand, in the case of an antiparallel configuration with a negligibly small
spacer, the Fano factor is $\sqrt{3 (1-P^2)}/4$, where $P$ denotes the
polarization of the conductivities. For $P\rightarrow \pm 1$, the current
through the system is almost noiseless.Comment: 5+ pages, 5 figures, including a short appendi

### Conductance of Interacting Quasi-One-Dimensional Electron Gas with a Scatterer

We calculate the conductance of a quantum wire with two occupied subbands in
a presence of a barrier taking into account the interaction between electrons.
We extend the renormalization-group equation for the scattering matrix of the
barrier to the case of intersubband interactions, find its fixed points, and
investigate their stability. Depending on the interaction parameters, the
conductance may be equal to 0, $e^2/h$, or $2e^2/h$ per spin projection. In
some parameter ranges, two stable fixed points may coexist, so the ultimate
conductance depends on the properties of the bare barrier. For spinful
electrons, the conductance of the wire may nonmonotonically depend on the Fermi
level and temperature.Comment: 9 pages, 4 figures, published versio

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