2,625 research outputs found
Multiple conducting carriers generated in LaAlO3/SrTiO3 heterostructures
We have found that there is more than one type of conducting carriers
generated in LaAlO3/SrTiO3 heterostructures by comparing the sheet carrier
density and mobility from optical transmission spectroscopy with those from
dc-transport measurements. When multiple types of carriers exist, optical
characterization dominantly reflects the contribution from the high-density
carriers whereas dc-transport measurements may exaggerate the contribution of
the high-mobility carriers even though they are present at low-density. Since
the low-temperature mobilities determined by dc-transport in the LaAlO3/SrTiO3
heterostructures are much higher than those extracted by optical method, we
attribute the origin of high-mobility transport to the low-density conducting
carriers.Comment: 3 figures, supplemental materia
DC--Transport in Quantum Wires
The influence of electron--electron interaction on two terminal DC
conductance of one--dimensional quantum wires is studied. A cancelation between
the effect of the electron--electron interaction on the current and on the
external electric field is the reason for the universal value,
per mode, of the DC conductance of a clean wire. The effect of the
renormalization of the electric field on the DC conductance in the presence of
an interplay between the electron--electron interaction and backward scattering
due to an impurity is considered.Comment: 11 Pages, Revte
On the character of states near the Fermi level in (Ga,Mn)As: impurity to valence band crossover
We discuss the character of states near the Fermi level in Mn doped GaAs, as
revealed by a survey of dc transport and optical studies over a wide range of
Mn concentrations. A thermally activated valence band contribution to dc
transport, a mid-infrared peak at energy hbar omega approx 200 meV in the ac-
conductivity, and the hot photoluminescence spectra indicate the presence of an
impurity band in low doped (<<1% Mn) insulating GaAs:Mn materials. Consistent
with the implications of this picture, both the impurity band ionization energy
inferred from the dc transport and the position of the mid-infrared peak move
to lower energies and the peak broadens with increasing Mn concentration. In
metallic materials with > 2% doping, no traces of Mn-related activated
contribution can be identified in dc-transport, suggesting that the impurity
band has merged with the valence band. No discrepancies with this perception
are found when analyzing optical measurements in the high-doped GaAs:Mn. A
higher energy (hbar omega approx 250 meV) mid-infrared feature which appears in
the metallic samples is associated with inter-valence band transitions. Its
red-shift with increased doping can be interpreted as a consequence of
increased screening which narrows the localized-state valence-band tails and
weakens higher energy transition amplitudes. Our examination of the dc and ac
transport characteristics of GaAs:Mn is accompanied by comparisons with its
shallow acceptor counterparts, confirming the disordered valence band picture
of high-doped metallic GaAs:Mn material.Comment: 10 pages, 12 figure
Unconventional dc transport in Rashba electron gases
We discuss the transport properties of a disordered two-dimensional electron
gas with strong Rashba spin-orbit coupling. We show that in the high-density
regime where the Fermi energy overcomes the energy associated with spin-orbit
coupling, dc transport is accurately described by a standard Drude's law, due
to a non-trivial compensation between the suppression of back-scattering and
the relativistic correction to the quasi-particle velocity. On the contrary,
when the system enters the opposite dominant spin-orbit regime, Drude's
paradigm breaks down and the dc conductivity becomes strongly sensitive to the
spin-orbit coupling strength, providing a suitable tool to test the
entanglement between spin and charge degrees of freedom in theseComment: 6 pages, 4 figures+Supplemental Material. To appear in Phys. Rev.
Let
Probing (topological) Floquet states through DC transport
We consider the differential conductance of a periodically driven system
connected to infinite electrodes. We focus on the situation where the
dissipation occurs predominantly in these electrodes. Using analytical
arguments and a detailed numerical study we relate the differential
conductances of such a system in two and three terminal geometries to the
spectrum of quasi-energies of the Floquet operator. Moreover these differential
conductances are found to provide an accurate probe of the existence of gaps in
this quasi-energy spectrum, being quantized when topological edge states occur
within these gaps. Our analysis opens the perspective to describe the
intermediate time dynamics of driven mesoscopic conductors as topological
Floquet filters.Comment: 8 pages, 6 figures, invited contribution to the special issue of
Physica E on "Frontiers in quantum electronic transport" in memory of Markus
Buttike
Ward identities for extended objects
Ward identities for extended objects are discussed. In the limit of dc
transport it is rigorously proved that charge-density and spin-density
fluctuations do not couple to electromagnetic field
Superconducting crossed correlations in ferromagnets: implications for thermodynamics and quantum transport
It is demonstrated that non local Cooper pairs can propagate in ferromagnetic
electrodes having an opposite spin orientation. In the presence of such crossed
correlations, the superconducting gap is found to depend explicitly on the
relative orientation of the ferromagnetic electrodes. Non local Cooper pairs
can in principle be probed with dc-transport. With two ferromagnetic
electrodes, we propose a ``quantum switch'' that can be used to detect
correlated pairs of electrons. With three or more ferromagnetic electrodes, the
Cooper pair-like state is a linear superposition of Cooper pairs which could be
detected in dc-transport. The effect also induces an enhancement of the
ferromagnetic proximity effect on the basis of crossed superconducting
correlations propagating along domain walls.Comment: 4 pages, RevTe
Sum rule for transport in a Luttinger liquid with long range interaction in the presence of an impurity
We show that the non-linear dc transport in a Luttinger liquid with
interaction of finite range in the presence of an impurity is governed by a sum
rule which causes the charging energy to vanish.Comment: 5 pages, RevTeX, 1 figure, to be published in Europhysics Letter
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