Charge-vibration interaction effects in normal-superconductor quantum dots

Anno: 2017

Autori: Stadler P., Belzig W., Rastelli G.

Affiliazione autori: Univ Konstanz, Fachbereich Phys, D-78457 Constance, Germany. Univ Konstanz, Zukunftskolleg & Fachbereich Phys, D-78457 Constance, Germany.

Abstract: We study the quantum transport and the nonequilibrium vibrational states of a quantum dot embedded between a normal-conducting and a superconducting lead with the charge on the quantum dot linearly coupled to a harmonic oscillator of frequency omega. To the leading order in the charge-vibration interaction, we calculate the current and the nonequilibrium phonon occupation by the Keldsyh Green´s function technique. We analyze the inelastic, vibration-assisted tunneling processes in the regime omega>omega. We also found that inelastic vibration-assisted Andreev reflections as well as quasiparticle tunneling induce a strong nonequilibrium state of the oscillator. In different ranges on the dot´s level, we found that the current produces: ( i) ground-state cooling of the oscillator with phonon occupation n << 1, ( ii) accumulation of energy in the oscillator with n >> 1, and ( iii) a mechanical instability characterized by a negative damping coefficient. We show that ground-state cooling is achieved simultaneously for several modes of different frequencies. Finally, we discuss how the nonequilibrium vibrational state can be readily detected by the asymmetric behavior of the inelastic current peaks with respect to the gate voltage.

Giornale/Rivista: PHYSICAL REVIEW B

Volume: 96 (4)      Da Pagina: 045429  A: 045429

Maggiori informazioni: We acknowledge J. C. Cuevas, E. Scheer, S. Andergassen, and T. Pietsch for interesting discussions and useful comments. This research was supported by the Zukunftskolleg of the University of Konstanz and by the DFG through the collaborative research center SFB 767.
Parole chiavi: quantum dots, quantum electromechanical systems, Andreev states
DOI: 10.1103/PhysRevB.96.045429

Citazioni: 12
dati da “WEB OF SCIENCE” (of Thomson Reuters) aggiornati al: 2025-01-12
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