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Title: X-shaped and Y-shaped Andreev resonance profiles in a superconducting quantum dot

The quasi-bound states of a superconducting quantum dot that is weakly coupled to a normal metal appear as resonances in the Andreev reflection probability, measured via the differential conductance. We study the evolution of these Andreev resonances when an external parameter (such as the magnetic field or gate voltage) is varied, using a random-matrix model for the N × N scattering matrix. We contrast the two ensembles with broken time-reversal symmetry, in the presence or absence of spin-rotation symmetry (class C or D). The poles of the scattering matrix in the complex plane, encoding the center and width of the resonance, are repelled from the imaginary axis in class C. In class D, in contrast, a number ∝ √N of the poles has zero real part. The corresponding Andreev resonances are pinned to the middle of the gap and produce a zero-bias conductance peak that does not split over a range of parameter values (Y-shaped profile), unlike the usual conductance peaks that merge and then immediately split (X-shaped profile)
Authors:
; ; ;  [1]
  1. Universiteit Leiden, Instituut-Lorentz (Netherlands)
Publication Date:
OSTI Identifier:
22472484
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Experimental and Theoretical Physics; Journal Volume: 119; Journal Issue: 6; Other Information: Copyright (c) 2014 Pleiades Publishing, Inc.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; BOUND STATE; MAGNETIC FIELDS; METALS; PROBABILITY; QUANTUM DOTS; RANDOMNESS; REFLECTION; RESONANCE; SCATTERING; SPIN; SUPERCONDUCTIVITY; SUPERCONDUCTORS; SYMMETRY