4,183 research outputs found
Quantum Hall Effect at Finite Temperatures
Recent work on the temperature-driven delocalization in the quantum Hall
regime is reviewed, with emphasis on the role of electron-electron interactions
and the correlation properties of disorder. We have stressed (i) the crucial
role of the Coulomb interaction in the integer quantum Hall effect; (ii) the
classical aspects of electron dynamics in samples with long-range disorder.Comment: 10 pages, LaTeX, uses sprocl.sty which is included, talk given at the
12th conference on High Magnetic Fields in Semiconductor Physics held in
Wuerzburg on July 28 - Aug 02, 199
Transport of charge-density waves in the presence of disorder: Classical pinning vs quantum localization
We consider the interplay of the elastic pinning and the Anderson
localization in the transport properties of a charge-density wave in one
dimension, within the framework of the Luttinger model in the limit of strong
repulsion. We address a conceptually important issue of which of the two
disorder-induced phenomena limits the mobility more effectively. We argue that
the interplay of the classical and quantum effects in transport of a very rigid
charge-density wave is quite nontrivial: the quantum localization sets in at a
temperature much smaller than the pinning temperature, whereas the quantum
localization length is much smaller than the pinning length.Comment: 4 page
Electron transport in disordered Luttinger liquid
We study the transport properties of interacting electrons in a disordered
quantum wire within the framework of the Luttinger liquid model. We demonstrate
that the notion of weak localization is applicable to the strongly correlated
one-dimensional electron system. Two alternative approaches to the problem are
developed, both combining fermionic and bosonic treatment of the underlying
physics. We calculate the relevant dephasing rate, which for spinless electrons
is governed by the interplay of electron-electron interaction and disorder,
thus vanishing in the clean limit. Our approach provides a framework for a
systematic study of mesoscopic effects in strongly correlated electron systems.Comment: 41 pages, 24 figures, small corrections, more compac
Many-body delocalization transition and relaxation in a quantum dot
We revisit the problem of quantum localization of many-body states in a
quantum dot and the associated problem of relaxation of an excited state in a
finite correlated electron system. We determine the localization threshold for
the eigenstates in Fock space. We argue that the localization-delocalization
transition (which manifests itself, e.g., in the statistics of many-body energy
levels) becomes sharp in the limit of a large dimensionless conductance (or,
equivalently, in the limit of weak interaction). We also analyze the temporal
relaxation of quantum states of various types (a "hot-electron state", a
"typical" many-body state, and a single-electron excitation added to a "thermal
state") with energies below, at, and above the transition.Comment: 16+6 pages, 2 figures; comments, additional explanations, references,
and Supplemental Material adde
Microwave photoconductivity of a 2D electron gas: Mechanisms and their interplay at high radiation power
We develop a systematic theory of microwave-induced oscillations in the
magnetoresistivity of a two-dimensional electron gas, focusing on the regime of
strongly overlapping Landau levels. At linear order in microwave power, two
novel mechanisms of the oscillations (``quadrupole'' and ``photovoltaic'') are
identified, in addition to those studied before (``displacement'' and
``inelastic''). The quadrupole and photovoltaic mechanisms are shown to be the
only ones that give rise to oscillations in the nondiagonal part of the
photoconductivity tensor. In the diagonal part, the inelastic contribution
dominates at moderate microwave power, while at elevated power the other
mechanisms become relevant. We demonstrate the crucial role of feedback
effects, which lead to a strong interplay of the four mechanisms in the
nonlinear photoresponse and yield, in particular, a nonmonotonic power
dependence of the photoconductivity, narrowing of the magnetoresonances, and a
nontrivial structure of the Hall photoresponse. At ultrahigh power, all effects
related to the Landau quantization decay due to a combination of the feedback
and multiphoton effects, restoring the classical Drude conductivity.Comment: 26 pages, 10 figures. V2: published version (typos corrected,
references updated
Cyclotron resonance harmonics in the ac response of a 2D electron gas with smooth disorder
The frequency-dependent conductivity of 2D electrons
subjected to a transverse magnetic field and smooth disorder is calculated. The
interplay of Landau quantization and disorder scattering gives rise to an
oscillatory structure that survives in the high-temperature limit. The relation
to recent experiments on photoconductivity by Zudov {\it et al.} and Mani {\it
et al.} is discussed.Comment: 4 pages, 2 figures; final version to appear in PR
Picture-changing operators and space-time supersymmetry
We explore geometrical properties of fermionic vertex operators for a NSR superstring in order to establish connection between worldsheet and target space supersymmetries. The mechanism of picture-changing is obtained as a result of imposing certain constraints on a world-sheet gauge group of the NSR theory. It is found that picture-changing operators of various integer ghost numbers form a polynomial ring. By using properties of the picture-changing formalism we establish connection between the NSR and GS superstring theories. We explore the properties of the \kappa-symmetry in the NSR formalism and show that it leads to some new identities between correlation functions
On the NSR formulation of String Theory on
We discuss the NSR formulation of the superstring action on AdS_5 X S^5 proposed recently by Kallosh and Tseytlin in the Green-Schwarz formalism.We show that the stress-energy tensor corresponding to the NSR action for AdS superstring contains the branelike terms, corresponding to exotic massless vertex operators (refered to as the branelike vertices). The corresponding sigma-model action has the manifest SO(1,3) X SO(6) invariance of AdS_5 X S^5. We argue that adding the branelike terms is equivalent to curving the space-time to obtain the AdS_5 X S^5 background. We commence the study of the proposed NSR sigma-model by analyzing the scattering amplitudes involving the branelike vertex operators.The analysis shows quite an unusual momentum dependence of these scattering amplitudes
Ultranarrow resonance in Coulomb drag between quantum wires at coinciding densities
We investigate the influence of the chemical potential mismatch
(different electron densities) on Coulomb drag between two parallel ballistic
quantum wires. For pair collisions, the drag resistivity
shows a peculiar anomaly at with being finite at
and vanishing at any nonzero . The "bodyless" resonance in
at zero is only broadened by processes of
multi-particle scattering. We analyze Coulomb drag for finite in the
presence of both two- and three-particle scattering within the kinetic equation
framework, focusing on a Fokker-Planck picture of the interaction-induced
diffusion in momentum space of the double-wire system. We describe the
dependence of on for both weak and strong intrawire
equilibration due to three-particle scattering.Comment: 21 pages (+2.5 pages Suppl. Mat.), 2 figures; additional explanation
Emergence of domains and nonlinear transport in the zero-resistance state
We study transport in the domain state, the so-called zero-resistance state,
that emerges in a two-dimensional electron system in which the combined action
of microwave radiation and magnetic field produces a negative absolute
conductivity. We show that the voltage-biased system has a rich phase diagram
in the system size and voltage plane, with second- and first-order transitions
between the domain and homogeneous states for small and large voltages,
respectively. We find the residual negative dissipative resistance in the
stable domain state.Comment: 5 pages, 4 figure
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