Dynamical multistability in a quantum-dot laser

We study a model for a single-atom laser implemented in a quantum dot spin valve. A resonator, consisting of a mechanical oscillator or a microwave cavity mode, interacts with two spin levels in a dot in contact with two ferromagnetic leads of antiparallel polarization. We prove that such a system encodes a single-atom laser where high-efficiency pumping is achieved by spin-polarized tunneling electrons. Moreover, the oscillator amplitude displays a multi-peaked distribution. This lasing multistability regime provides an opportunity to explore the effects of coherent spin-oscillator dynamics beyond the usual rotating-wave approximation at relatively weak couplings. The multistability manifests itself directly in the charge current flowing through the dot, switching between distinct current levels corresponding to the different states of oscillation.