94 research outputs found
Dephasing in Open Quantum Dots
Shape-averaged magnetoconductance (weak localization) is used for the first
time to obtain the electron phase coherence time in open
ballistic GaAs quantum dots. Values for in the range of
temperature T from 0.335 to 4 K are found to be independent of dot area, and
are not consistent with the behavior expected for
isolated dots. Surprisingly, agrees quantitatively with the
predicted dephasing time for disordered two-dimensional electron systems.Comment: 9 pages, 4 figure
Multicomponent theory of buoyancy instabilities in magnetized plasmas: The case of magnetic field parallel to gravity
We investigate electromagnetic buoyancy instabilities of the electron-ion
plasma with the heat flux based on not the magnetohydrodynamic (MHD) equations,
but using the multicomponent plasma approach when the momentum equations are
solved for each species. We consider a geometry in which the background
magnetic field, gravity, and stratification are directed along one axis. The
nonzero background electron thermal flux is taken into account. Collisions
between electrons and ions are included in the momentum equations. No
simplifications usual for the one-fluid MHD-approach in studying these
instabilities are used. We derive a simple dispersion relation, which shows
that the thermal flux perturbation generally stabilizes an instability for the
geometry under consideration. This result contradicts to conclusion obtained in
the MHD-approach. We show that the reason of this contradiction is the
simplified assumptions used in the MHD analysis of buoyancy instabilities and
the role of the longitudinal electric field perturbation which is not captured
by the ideal MHD equations. Our dispersion relation also shows that the medium
with the electron thermal flux can be unstable, if the temperature gradients of
ions and electrons have the opposite signs. The results obtained can be applied
to the weakly collisional magnetized plasma objects in laboratory and
astrophysics.Comment: Accepted for publication in Astrophysics & Space Scienc
Scanned Potential Microscopy of Edge States in a Quantum Hall Liquid
Using a low-temperature atomic force microscope as a local voltmeter, we
measure the Hall voltage profile in a quantum Hall conductor in the presence of
a gate-induced non-equilibrium edge state population at n=3. We observe sharp
voltage drops at the sample edges which are suppressed by re-equilibrating the
edge states.Comment: 4 pages, 4 figs. To be published in Physica E (Proceedings of the
13th International Conference on the Properties of 2D Systems
Statistical Theory of Spin Relaxation and Diffusion in Solids
A comprehensive theoretical description is given for the spin relaxation and
diffusion in solids. The formulation is made in a general
statistical-mechanical way. The method of the nonequilibrium statistical
operator (NSO) developed by D. N. Zubarev is employed to analyze a relaxation
dynamics of a spin subsystem. Perturbation of this subsystem in solids may
produce a nonequilibrium state which is then relaxed to an equilibrium state
due to the interaction between the particles or with a thermal bath (lattice).
The generalized kinetic equations were derived previously for a system weakly
coupled to a thermal bath to elucidate the nature of transport and relaxation
processes. In this paper, these results are used to describe the relaxation and
diffusion of nuclear spins in solids. The aim is to formulate a successive and
coherent microscopic description of the nuclear magnetic relaxation and
diffusion in solids. The nuclear spin-lattice relaxation is considered and the
Gorter relation is derived. As an example, a theory of spin diffusion of the
nuclear magnetic moment in dilute alloys (like Cu-Mn) is developed. It is shown
that due to the dipolar interaction between host nuclear spins and impurity
spins, a nonuniform distribution in the host nuclear spin system will occur and
consequently the macroscopic relaxation time will be strongly determined by the
spin diffusion. The explicit expressions for the relaxation time in certain
physically relevant cases are given.Comment: 41 pages, 119 Refs. Corrected typos, added reference
Observation of cyclotron-resonance in the photoconductivity of two-dimensional electrons
Contains fulltext :
115610.pdf (publisher's version ) (Open Access
Observation of oscillatory linewidth in the cyclotron-resonance of GaAs-AlxGa1-xAs heterostructures
Contains fulltext :
115600.pdf (publisher's version ) (Open Access
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