112 research outputs found
Dephasing-enabled triplet Andreev conductance
We study the conductance of normal-superconducting quantum dots with strong
spin-orbit scattering, coupled to a source reservoir using a single-mode
spin-filtering quantum point contact. The choice of the system is guided by the
aim to study triplet Andreev reflection without relying on half metallic
materials with specific interface properties. Focusing on the zero temperature,
zero-bias regime, we show how dephasing due to the presence of a voltage probe
enables the conductance, which vanishes in the quantum limit, to take nonzero
values. Concentrating on chaotic quantum dots, we obtain the full distribution
of the conductance as a function of the dephasing rate. As dephasing gradually
lifts the conductance from zero, the dependence of the conductance fluctuations
on the dephasing rate is nonmonotonic. This is in contrast to chaotic quantum
dots in usual transport situations, where dephasing monotonically suppresses
the conductance fluctuations.Comment: 6 pages, 3 figure
A basic optimization problem in linear systems
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/48017/1/224_2005_Article_BF01691464.pd
Relative asymptotics for orthogonal matrix polynomials with respect to a perturbed matrix measure on the unit circle
19 pages, no figures.-- MSC2000 codes: 42C05, 47A56.MR#: MR1970413 (2004b:42058)Zbl#: Zbl 1047.42021Given a positive definite matrix measure Ω supported on the unit circle T, then main purpose of this paper is to study the asymptotic behavior of L_n(\tilde{\Omega}) L_n(\Omega) -1} and \Phi_n(z, \tilde{\Omega}) \Phi_n(z, \tilde{\Omega}) -1} where , , M is a positive definite matrix and ÎŽ is the Dirac matrix measure. Here, Ln(·) means the leading coefficient of the orthonormal matrix polynomials Ίn(z; âą).Finally, we deduce the asymptotic behavior of in the case when M=I.The work of the second author was supported by DirecciĂłn General de Enseñanza Superior (DGES) of Spain under grant PB96-0120-C03-01 and INTAS
Project INTAS93-0219 Ext.Publicad
Problema H2/H<FONT FACE=Symbol>„</FONT>: soluçÔes aproximadas por meio de expansão em bases
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