Andreev reflection assisted lasing in an electromagnetic resonator coupled to a hybrid-quantum-dot

TL;DR

This paper theoretically investigates how Andreev reflections and Floquet-Andreev resonances enable lasing in a superconducting hybrid quantum dot coupled to an electromagnetic resonator, revealing conditions for different lasing mechanisms.

Contribution

It introduces a novel theoretical framework showing how Andreev reflections facilitate lasing in a hybrid quantum-dot system under non-equilibrium conditions.

Findings

Lasing occurs in the superconducting gap frequency range.

Lasing can be driven by single or cascaded electron transitions.

Resonant Andreev reflections enable non-zero gain spectrum.

Abstract

A single mode electromagnetic resonator coupled to a two-level hybrid-quantum-dot(hQD) is studied theoretically as a laser(maser), when the hQD is driven out of equilibrium with external applied d.c. bias voltage. Using the formalism of the non-equilibrium Green's functions for the hQD and the semi-classical laser equations, we determine the relevant physical quantities of the system. We find that due to the resonant Andreev reflections and the formation of the Floquet-Andreev side-resonances in the sub-gap region, at appropriate gate voltages and above a certain threshold bias voltage and damping factor of the resonator, the two-level QD has non-zero gain spectrum and lasing can happen in the system in the frequency range of superconducting gap. Furthermore, our results show that depending on the damping factor of the resonator and above a specific threshold bias voltages, the lasing can be either due to single electron transitions or cascaded electron transitions between the Andreev resonances and Floquet-Andreev side-resonances.