814 research outputs found
Electron-electron interactions in the conductivity of graphene
The effect of electron-electron interaction on the low-temperature
conductivity of graphene is investigated experimentally. Unlike in other
two-dimensional systems, the electron-electron interaction correction in
graphene is sensitive to the details of disorder. A new temperature regime of
the interaction correction is observed where quantum interference is suppressed
by intra-valley scattering. We determine the value of the interaction
parameter, F_0 ~ -0.1, and show that its small value is due to the chiral
nature of interacting electrons.Comment: 4 pages, 4 figures, 1 tabl
Giant Fluctuations of Coulomb Drag in a Bilayer System
We have observed reproducible fluctuations of the Coulomb drag, both as a
function of magnetic field and electron concentration, which are a
manifestation of quantum interference of electrons in the layers. At low
temperatures the fluctuations exceed the average drag, giving rise to random
changes of the sign of the drag. The fluctuations are found to be much larger
than previously expected, and we propose a model which explains their
enhancement by considering fluctuations of local electron properties.Comment: 10 pages, 4 figure
Enhanced fluctuations of the tunneling density of states near bottoms of Landau bands measured by a local spectrometer
We have found that the local density of states fluctuations (LDOSF) in a
disordered metal, detected using an impurity in the barrier as a spectrometer,
undergo enhanced (with respect to SdH and dHvA effects) oscillations in strong
magnetic fields, omega _c\tau > 1. We attribute this to the dominant role of
the states near bottoms of Landau bands which give the major contribution to
the LDOSF and are most strongly affected by disorder. We also demonstrate that
in intermediate fields the LDOSF increase with B in accordance with the results
obtained in the diffusion approximation.Comment: 4 pages, 4 figure
Re-entrant resonant tunneling
We study the effect of electron-electron interactions on the
resonant-tunneling spectroscopy of the localized states in a barrier. Using a
simple model of three localized states, we show that, due to the Coulomb
interactions, a single state can give rise to two resonant peaks in the
conductance as a function of gate voltage, G(Vg). We also demonstrate that an
additional higher-order resonance with Vg-position in between these two peaks
becomes possibile when interactions are taken into account. The corresponding
resonant-tunneling process involves two-electron transitions. We have observed
both these effects in GaAs transistor microstructures by studying the time
evolution of three adjacent G(Vg) peaks caused by fluctuating occupation of an
isolated impurity (modulator). The heights of the two stronger peaks exibit
in-phase fluctuations. The phase of fluctuations of the smaller middle peak is
opposite. The two stronger peaks have their origin in the same localized state,
and the third one corresponds to a co-tunneling process.Comment: 9 pages, REVTeX, 4 figure
Transfer of momentum and torque from a light beam to a liquid
Refraction or absorption of light results in the force and torque, i.e., transfer of momentum and angular momentum from light to the medium. In transversely inhomogeneous beams, the force per unit volume f may have curlf not equal 0 leading to flow or to nonthermal and nongravitational convection in liquids. The force and the torque in scattering systems are as strong as in absorbing materials and may allow one to carry out experiments avoiding thermal effects. Nonlinear optical response of liquid crystals due to this convection is discussed
Quantum transport thermometry for electrons in graphene
We propose a method of measuring the electron temperature in mesoscopic
conductors and demonstrate experimentally its applicability to micron-size
graphene devices in the linear-response regime (, the bath
temperature). The method can be {especially useful} in case of overheating,
. It is based on analysis of the correlation function of mesoscopic
conductance fluctuations. Although the fluctuation amplitude strongly depends
on the details of electron scattering in graphene, we show that extracted
from the correlation function is insensitive to these details.Comment: 4 pages, 4 figures; final version, as publishe
A dynamic localization of 2D electrons at mesoscopic length scales
We have investigated the local magneto-transport in high-quality 2D electron
systems at low carrier densities. The positive magneto-resistance in
perpendicular magnetic field in the strongly insulating regime has been
measured to evaluate the spatial concentration of localized states within a
mesoscopic region of the samples. An independent measurement of the electron
density within the same region shows an unexpected correspondence between the
density of electrons in the metallic regime and that of the localized states in
the insulating phase. We have argued that this correspondence manifests a rigid
distribution of electrons at low densities.Comment: 8 pages (incl 4 figures), double colum
Hard-core Radius of Nucleons within the Induced Surface Tension Approach
In this work we discuss a novel approach to model the hadronic and nuclear
matter equations of state using the induced surface tension concept. Since the
obtained equations of state, classical and quantum, are among the most
successful ones in describing the properties of low density phases of strongly
interacting matter, they set strong restrictions on the possible value of the
hard-core radius of nucleons. Therefore, we perform a detailed analysis of its
value which follows from hadronic and nuclear matter properties and find the
most trustworthy range of its values: the hard-core radius of nucleons is
0.30--0.36 fm. A comparison with the phenomenology of neutron stars implies
that the hard-core radius of nucleons has to be temperature and density
dependent.Comment: 12 pages, 4 figures, references added, typos correcte
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