690 research outputs found
Intrinsic optical dichroism in the chiral superconducting state of SrRuO
We present an analysis of the Hall conductivity in
time reversal symmetry breaking states of exotic superconductors. We find that
the dichroic signal is non-zero in systems with inter-band order parameters.
This new intrinsic mechanism may explain the Kerr effect observed in strontium
ruthenate and possibly other superconductors. We predict coherence factor
effects in the temperature dependence of the imaginary part of the ac Hall
conductivity , which can be tested experimentally.Comment: 4+ pages, 4 figures, published versio
The Kerr rotation in the unconventional superconductor SrRuO
The interpretation of Kerr rotation measurements in the superconducting phase
of SrRuO is a controversial topic. Both intrinsic and extrinsic
mechanisms have been proposed, and it has been argued that the intrinsic
response vanishes by symmetry. We focus on the intrinsic contribution and
clarify several conflicting results in the literature. On the basis of symmetry
considerations and detailed calculations we show that the intrinsic Kerr signal
is not forbidden in a general multi- band system but has a rich structure in
the near infrared regime. We distinguish different optical transitions
determined by the superconducting gap (far infrared) and the inter orbital
coupling of the normal state (near infrared). We argue that the low frequency
transitions do not contribute to the Hall conductivity while only the
inter-orbital transitions in the near infrared regime contribute. Finally, we
discuss the difficulties to connect the calculations for the optical Hall
conductivity to the experimental measurement of the Kerr angle. We will compare
different approximations which might lead to conflicting results.Comment: 9 pages, 8 figures, 1 tabl
Box and Gaussian plume models of the exhaust composition evolution of subsonic transport aircraft in- and out of the flight corridor
Distribution of G-concurrence of random pure states
Average entanglement of random pure states of an N x N composite system is
analyzed. We compute the average value of the determinant D of the reduced
state, which forms an entanglement monotone. Calculating higher moments of the
determinant we characterize the probability distribution P(D). Similar results
are obtained for the rescaled N-th root of the determinant, called
G-concurrence. We show that in the limit this quantity becomes
concentrated at a single point G=1/e. The position of the concentration point
changes if one consider an arbitrary N x K bipartite system, in the joint limit
, K/N fixed.Comment: RevTeX4, 11 pages, 4 Encapsuled PostScript figures - Introduced new
results, Section II and V have been significantly improved - To appear on PR
Stationary states for underdamped anharmonic oscillators driven by Cauchy noise
Using methods of stochastic dynamics, we have studied stationary states in
the underdamped anharmonic stochastic oscillators driven by Cauchy noise. Shape
of stationary states depend both on the potential type and the damping. If the
damping is strong enough, for potential wells which in the overdamped regime
produce multimodal stationary states, stationary states in the underdamped
regime can be multimodal with the same number of modes like in the overdamped
regime. For the parabolic potential, the stationary density is always unimodal
and it is given by the two dimensional -stable density. For the mixture
of quartic and parabolic single-well potentials the stationary density can be
bimodal. Nevertheless, the parabolic addition, which is strong enough, can
destroy bimodlity of the stationary state.Comment: 9 page
Coarse-grained entanglement classification through orthogonal arrays
Classification of entanglement in multipartite quantum systems is an open
problem solved so far only for bipartite systems and for systems composed of
three and four qubits. We propose here a coarse-grained classification of
entanglement in systems consisting of subsystems with an arbitrary number
of internal levels each, based on properties of orthogonal arrays with
columns. In particular, we investigate in detail a subset of highly entangled
pure states which contains all states defining maximum distance separable
codes. To illustrate the methods presented, we analyze systems of four and five
qubits, as well as heterogeneous tripartite systems consisting of two qubits
and one qutrit or one qubit and two qutrits.Comment: 38 pages, 1 figur
Invariant sets for discontinuous parabolic area-preserving torus maps
We analyze a class of piecewise linear parabolic maps on the torus, namely
those obtained by considering a linear map with double eigenvalue one and
taking modulo one in each component. We show that within this two parameter
family of maps, the set of noninvertible maps is open and dense. For cases
where the entries in the matrix are rational we show that the maximal invariant
set has positive Lebesgue measure and we give bounds on the measure. For
several examples we find expressions for the measure of the invariant set but
we leave open the question as to whether there are parameters for which this
measure is zero.Comment: 19 pages in Latex (with epsfig,amssymb,graphics) with 5 figures in
eps; revised version: section 2 rewritten, new example and picture adde
Eliashberg-type equations for correlated superconductors
The derivation of the Eliashberg -- type equations for a superconductor with
strong correlations and electron--phonon interaction has been presented. The
proper account of short range Coulomb interactions results in a strongly
anisotropic equations. Possible symmetries of the order parameter include s, p
and d wave. We found the carrier concentration dependence of the coupling
constants corresponding to these symmetries. At low hole doping the d-wave
component is the largest one.Comment: RevTeX, 18 pages, 5 ps figures added at the end of source file, to be
published in Phys.Rev. B, contact: [email protected]
Random graph states, maximal flow and Fuss-Catalan distributions
For any graph consisting of vertices and edges we construct an
ensemble of random pure quantum states which describe a system composed of
subsystems. Each edge of the graph represents a bi-partite, maximally entangled
state. Each vertex represents a random unitary matrix generated according to
the Haar measure, which describes the coupling between subsystems. Dividing all
subsystems into two parts, one may study entanglement with respect to this
partition. A general technique to derive an expression for the average
entanglement entropy of random pure states associated to a given graph is
presented. Our technique relies on Weingarten calculus and flow problems. We
analyze statistical properties of spectra of such random density matrices and
show for which cases they are described by the free Poissonian
(Marchenko-Pastur) distribution. We derive a discrete family of generalized,
Fuss-Catalan distributions and explicitly construct graphs which lead to
ensembles of random states characterized by these novel distributions of
eigenvalues.Comment: 37 pages, 24 figure
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