Dynamical multistability in a quantum-dot laser*

Quantum dots coupled to microwave cavities or nanomechanical resonators allow to investigate novel regimes of electron-phonon and electron-photon interactions, because of their highly tailorable properties. Here, we consider a hybrid implementation of a single-atom laser [1], where a quantum dot with two spin-split levels is coupled to a harmonic resonator and is embedded between two ferromagnetic contacts with opposite polarization. A spin-polarized current driven through the dot brings the resonator in a highly-excited lasing state. We show that the high efficiency of this pumping mechanism breaks the rotating-wave approximation (RWA) usually employed for the laser, without any need of ultrastrong spin-resonator coupling. Remarkably, the oscillator displays a rich multistable regime characterized by a multi-peaked Fock distribution. Multistability can be detected by monitoring the current in time, as it switches between distinct current levels corresponding to different states of oscillation [2].
[1] Y. Mu, M. Savage, PRA 46, 5944 (1992).
[2] M. Mantovani, A. Armour, W. Belzig, and G. Rastelli, PRB 99, 045442 (2019).