A phonon laser utilizing quantum-dot spin states

TL;DR

This paper proposes a nano-scale phonon laser using quantum-dot spin states to amplify sound, leveraging long spin relaxation times and phonon confinement to achieve efficient stimulated emission.

Contribution

It introduces a novel phonon laser design based on quantum-dot spin flips, emphasizing the benefits of strong pumping and phonon confinement in nanowire structures.

Findings

Long spin relaxation times enable high population inversion.

Phonon confinement in nanowires reduces spontaneous emission modes.

Threshold for stimulated emission remains unaffected by spontaneous spin flips.

Abstract

We propose a nano-scale realization of a phonon laser utilizing phonon-assisted spin flips in quantum dots to amplify sound. Owing to a long spin relaxation time, the device can be operated in a strong pumping regime, in which the population inversion is close to its maximal value allowed under Fermi statistics. In this regime, the threshold for stimulated emission is unaffected by spontaneous spin flips. Considering a nanowire with quantum dots defined along its length, we show that a further improvement arises from confining the phonons to one dimension, and thus reducing the number of phonon modes available for spontaneous emission. Our work calls for the development of nanowire-based, high-finesse phonon resonators.