447 research outputs found
Proximity Action theory of superconductive nanostructures
We review a novel approach to the superconductive proximity effect in
disordered normal-superconducting (N-S) structures. The method is based on the
multicharge Keldysh action and is suitable for the treatment of interaction and
fluctuation effects. As an application of the formalism, we study the subgap
conductance and noise in two-dimensional N-S systems in the presence of the
electron-electron interaction in the Cooper channel. It is shown that singular
nature of the interaction correction at large scales leads to a nonmonotonuos
temperature, voltage and magnetic field dependence of the Andreev conductance.Comment: RevTeX, 6 pages, 5 eps figures. This is a concise review of
cond-mat/0008463; to be published in the Proceedings of the conference
"Mesoscopic and strongly correlated electron systems" (Chernogolovka, Russia,
July 2000
Dyson-Maleev representation of nonlinear sigma-models
For nonlinear sigma-models in the unitary symmetry class, the non-linear
target space can be parameterized with cubic polynomials. This choice of
coordinates has been known previously as the Dyson-Maleev parameterization for
spin systems, and we show that it can be applied to a wide range of
sigma-models. The practical use of this parameterization includes
simplification of diagrammatic calculations (in perturbative methods) and of
algebraic manipulations (in non-perturbative approaches). We illustrate the use
and specific issues of the Dyson-Maleev parameterization with three examples:
the Keldysh sigma-model for time-dependent random Hamiltonians, the
supersymmetric sigma-model for random matrices, and the supersymmetric
transfer-matrix technique for quasi-one-dimensional disordered wires. We
demonstrate that nonlinear sigma-models of unitary-like symmetry classes C and
B/D also admit the Dyson-Maleev parameterization.Comment: 16 pages, 1 figur
Interference induced metallic-like behavior of a two-dimensional hole gas in asymmetric GaAs/InGaAs/GaAs quantum well
The temperature and magnetic field dependences of the conductivity of the
heterostructures with asymmetric InGaAs quantum well are studied.
It is shown that the metallic-like temperature dependence of the conductivity
observed in the structures investigated is quantitatively understandable within
the whole temperature range, K. It is caused by the interference
quantum correction at fast spin relaxation for 0.4 K K. At higher
temperatures, 1.5 K K, it is due to the interaction quantum correction.
Finally, at K, the metallic-like behavior is determined by the phonon
scattering.Comment: 4 pages, 4 figure
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