Phase-dependent magnetoconductance fluctuations in a chaotic Josephson junction

P. W. Brouwer; C. W. J. Beenakker

doi:10.1103/PhysRevB.54.R12705

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Phase-dependent magnetoconductance fluctuations in a chaotic Josephson junction

P. W. Brouwer, C. W. J. Beenakker

DOI 10.1103/PhysRevB.54.R12705 · Physical Review B

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Abstract

Motivated by recent experiments by Den Hartog et al., we present a random-matrix theory for the magnetoconductance fluctuations of a chaotic quantum dot that is coupled by point contacts to two superconductors and one or two normal metals. There are aperiodic conductance fluctuations as a function of the magnetic field through the quantum dot and 2π-periodic fluctuations as a function of the phase difference φ of the superconductors. If the coupling to the superconductors is weak compared to the coupling to the normal metals, the φ dependence of the conductance is harmonic, as observed in the experiment. In the opposite regime, the conductance becomes a random 2π-periodic function of φ, in agreement with the theory of Altshuler and Spivak. The theoretical method employs an extension of the circular ensemble which can describe the magnetic-field dependence of the scattering matrix.