Dresden 2017 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 76: Poster Session: Transport 2

TT 76.1: Poster

Donnerstag, 23. März 2017, 15:00–19:00, P2-OG1

Vibrational lasing in a nanomechanical resonator by spin-polarized current — •Mattia Mantovani¹, Andrew Armour², Wolfgang Belzig¹, and Gianluca Rastelli¹ — ¹Fachbereich Physik, Universität Konstanz, D-78457 Konstanz, Germany — ²School of Physics and Astronomy, University of Nottingham, NG7 2RD Nottingham, United Kingdom

We study the nonequilibrium dynamics of a nanomechanical resonator, realized by a suspended carbon nanotube quantum dot in contact with two ferromagnetic leads, in which the dot’s spin is coupled to the vibrational flexural modes [1, 2]. We show that, for an appropriate configuration of the two dot’s spin levels and orientation of the magnetization in the leads, the system encodes a single-atom laser [3] where the mechanical vibration plays the role of the cavity, with frequency equal to the Zeeman splitting of the two levels. Moreover, such a system has unique features, as one can not neglect the effects of: (i) finite temperature for such low-frequency resonators (< 100 MHz) and (ii) the nonlinear forces for strong, amplified amplitudes of oscillation. To understand how these effects modify the physics of the single-atom laser, we solve numerically the associated Lindblad equation to compute the average phonon occupation, the Fano factor and the spin-polarized current as a function of the bias voltage and other parameters. We show that the lasing threshold is within the experimental range for magnetic polarization and spin-vibration coupling strength.

[1] P. Stadler et al., PRL 113, 047201 (2014); PRB 91, 085432 (2015)

[2] A. Pályi et al., PRL 108, 206811 (2012)

[3] Y. Mu, M. Savage, PRA 46, 5944 (1992).