laboratoire pierre aigrain
électronique et photonique quantiques
laboratoire pierre aigrain

Seminar, 25 Sep 2017 (13h30 salle à confirmer)

Régis Mélin, Institut Néél, Grenoble
Nonequilibrium generalization of Andreev bound states

Three superconductors contacted within a narrow region form a three-terminal Josephson junction, controlled by two independent voltages, and by two independent phase differences. Coherent DC multipair currents can flow at resonance, for commensurate voltage bias values [1,2]. A simple physical picture of the steady state will be developed [3], using Floquet theory. The later will be introduced on the example of a driven qu-bit, starting from the rotating wave approximation, and going beyond with Floquet theory. The equilibrium Andreev bound states (for V=0) evolve into nonequilibrium Floquet-Wannier-Stark-Andreev (FWS-Andreev) ladders of resonances (for non-zero V). Those resonances acquire a finite width due to multiple Andreev reflection processes. The effect of an extrinsic line-width broadening on the quantum dot will also be considered, and introduced through a Dynes phenomenological parameter. The dc-quartet current manifests a crossover between the extrinsic relaxation dominated regime at low voltage to an intrinsic relaxation due to MAR processes at higher voltage. Three important low-energy scales will be identified, and a perspective is to relate those low-energy scales to the cross-correlation experiment of the Weizmann group [4,5].

[1] A. Freyn, B. Douçot, D. Feinberg and R. Mélin, Phys. Rev. Lett. 106, 257005 (2011)

[2] R. Mélin, D. Feinberg and B. Douçot, Eur. Phys. J. B 89:67 (2016)

[3] R. Mélin, J.-G. Caputo, K. Yang and B. Douçot, Phys. Rev. B 95, 085415 (2017)

[4] R. Mélin, M. Sotto, D. Feinberg, J.-G. Caputo and B. Douçot, Phys. Rev. B 93, 115436 (2016)

[5] Y. Cohen, Y. Ronen, J.-H. Kang, M. Heiblum, D. Feinberg, R. Mélin and H. Shtrikman, arXiv:1606:08441