Abstract
We study the dynamical multistability of a solid-state single-atom laser implemented in a quantum-dot spin valve. The system is formed by a resonator that interacts with a two-level system in a dot in contact with two ferromagnetic leads of antiparallel polarization. We show that a spin-polarized current provides high-efficiency pumping leading to regimes of multistable lasing, in which the Fock distribution of the oscillator displays a multi-peaked distribution. The emergence of multistable lasing follows from the breakdown of the usual rotating-wave approximation for the coherent spin-resonator interaction which occurs 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.
Highlights
Quantum conductors coupled to localized harmonic resonators, such as microwave photon cavities [1,2,3,4,5,6] or mechanical resonators [7,8,9,10] have become commonly studied systems
We have analyzed a model quantum dot spin valve which forms an unconventional single-atom laser: a spin-polarized current pumps the motion of a resonator coupled to the dot very efficiently, allowing access to novel regimes of multistable lasing
We show that multistability develops when the dot-resonator interaction is no longer captured by the conventional rotating-wave approximation (RWA)—which is expected to occur for the relatively weak couplings achievable with current devices—because large amplitude motion of the resonator enhances the effective coupling strength
Summary
Quantum conductors coupled to localized harmonic resonators, such as microwave photon cavities [1,2,3,4,5,6] or mechanical resonators [7,8,9,10] have become commonly studied systems They open the route to explore correlations between charge transport and emitted radiation [11] or induced mechanical vibrations [12]. Lasers where a cavity mode interacts with a stream of excited atoms one at a time [13, 14] can display multistability [18], whereby two or more stable amplitudes of oscillation coexist Such behavior has been predicted to occur in solid-state analogues, such as single-electron transistors [19,20,21,22] and optomechanical systems [23, 24].
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