Lasing and antibunching of optical phonons in semiconductor double quantum dots

TL;DR

This paper theoretically demonstrates optical phonon lasing and antibunching in semiconductor double quantum dots, showing how electron-phonon interactions lead to non-equilibrium phonon states without external cavities.

Contribution

It introduces a natural cavity formed by optical phonon modes in DQDs and analyzes conditions for phonon lasing and antibunching using a rate equation approach.

Findings

Lasing occurs when electron tunneling rate exceeds phonon decay rate.

Phonon antibunching appears in the opposite tunneling regime.

Strong electron-phonon coupling can thermalize phonons, suppressing effects.

Abstract

We theoretically propose optical phonon lasing in a double quantum dot (DQD) fabricated on a semiconductor substrate. No additional cavity or resonator is required. An electron in the DQD is found to be coupled to only two longitudinal optical phonon modes that act as a natural cavity. When the energy level spacing in the DQD is tuned to the phonon energy, the electron transfer is accompanied by the emission of the phonon modes. The resulting non-equilibrium motion of electrons and phonons is analyzed by the rate equation approach based on the Born-Markov-Secular approximation. We show that the lasing occurs for pumping the DQD via electron tunneling at rate much larger than the phonon decay rate, whereas a phonon antibunching is observed in the opposite regime of slow tunneling. Both effects disappear by an effective thermalization induced by the Franck-Condon effect in a DQD fabricated in a suspended carbon nanotube with strong electron-phonon coupling.