211 research outputs found
Winding angle distribution of 2D random walks with traps
We study analytically the asymptotic behaviour of the average probability
P(n,t) for the trajectory of a 2D Brownian particle wandering in the presence
of randomly distributed traps to wind n times around a given point after a time
t. It is shown that P(n,t)\sim\exp(-c\sqrt{t}) (1+x^2)^{-1} with x\sim
n/\sqrt{t}, where the first exponent represents a well known long-time tail of
the probability that a particle will not be trapped.Comment: RevTeX, 6 pages, 1 postscript figure, to be published in J. Phys.
Persistent current in a mesoscopic ring with diffuse surface scattering
The persistent current in a clean mesoscopic ring with ballistic electron
motion is calculated. The particle dynamics inside a ring is assumed to be
chaotic due to scattering at the surface irregularities of atomic size. This
allows one to use the so-called ``ballistic'' supersymmetric \sigma model for
calculation of the two-level correlation function in the presence of a nonzero
magnetic flux.Comment: REVTeX, 4 pages; to be published in PRB (June 1999
Impurity resonances in the mixed state of high-Tc superconductors
We study the quasiparticle resonance states near strong impurities in the
mixed state of a d-wave superconductor. These states give rise to zero-bias
peaks in the local density of states, observed in scanning tunneling microscopy
experiments. The field dependence of the peaks is obtained by averaging with
respect to the spatially non-uniform Doppler shifts in the energy of
excitations. The hybridization of the magnetic field-induced nodal
quasiparticles with the impurity resonances results in the suppression and
broadening of the zero-bias peaks. The height of the peaks is found to scale as
\sqrt{Hc2/H}. The magnetic field response of the peaks is shown to be strongly
dependent on the field orientation
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