8 research outputs found
Low temperature magnetoresistance of dirty thin films and quantum wires near a parallel-field-tuned superconducting quantum phase transition
We study the low temperature magnetoresistance of dirty thin films and
quantum wires close to a quantum phase transition from a superconducting to
normal state, induced by applying a parallel magnetic field. We find that the
different corrections (Aslamazov-Larkin, density of states and Maki-Thompson)
to the normal state conductivity, coming from the superconducting pair
fluctuations, are of the same order at zero temperature. There are three
regimes at finite temperatures. In the "quantum" regime, which essentially
shows a zero-temperature-like behavior we find a negative magnetoresistance.
Since in the "classical" regime the correction is positive, we predict a
non-monotonic magnetoresistance at higher temperatures.Comment: Proceedings for SCES conference (2004
Enhancement of fusion rates due to quantum effects in the particles momentum distribution in nonideal media
This study concerns a situation when measurements of the nonresonant
cross-section of nuclear reactions appear highly dependent on the environment
in which the particles interact. An appealing example discussed in the paper is
the interaction of a deuteron beam with a target of deuterated metal Ta. In
these experiments, the reaction cross section for d(d,p)t was shown to be
orders of magnitude greater than what the conventional model predicts for the
low-energy particles. In this paper we take into account the influence of
quantum effects due to the Heisenberg uncertainty principle for particles in a
non-ideal medium elastically interacting with the medium particles. In order to
calculate the nuclear reaction rate in the non-ideal environment we apply both
the Monte Carlo technique and approximate analytical calculation of the Feynman
diagram using nonrelativistic kinetic Green's functions in the medium which
correspond to the generalized energy and momentum distribution functions of
interacting particles. We show a possibility to reduce the 12-fold integral
corresponding to this diagram to a fivefold integral. This can significantly
speed up the computation and control accuracy. Our calculations show that
quantum effects significantly influence reaction rates such as p +7Be, 3He
+4He, p +7Li, and 12C +12C. The new reaction rates may be much higher than the
classical ones for the interior of the Sun and supernova stars. The possibility
to observe the theoretical predictions under laboratory conditions is
discussed
Electron transport and energy relaxation in dilute magnetic alloys
We consider the effect of the RKKY interaction between magnetic impurities on
the electron relaxation rates in a normal metal. The interplay between the RKKY
interaction and the Kondo effect may result in a non-monotonic temperature
dependence of the electron momentum relaxation rate, which determines the Drude
conductivity. The electron phase relaxation rate, which determines the
magnitude of the weak localization correction to the resistivity, is also a
non-monotonic function of temperature. For this function, we find the
dependence of the position of its maximum on the concentration of magnetic
impurities. We also relate the electron energy relaxation rate to the
excitation spectrum of the system of magnetic impurities. The energy relaxation
determines the distribution function for the out-of-equilibrium electrons.
Measurement of the electron distribution function thus may provide information
about the excitations in the spin glass phase.Comment: 15 pages, 5 figure
Electronic properties and quantum transport in Graphene-based nanostructures
61.46.-w Structure of nanoscale materials, 73.63.-b Electronic transport in nanoscale materials and structures,