Coherent interaction of a-few-electron quantum dot with a terahertz optical resonator

TL;DR

This study demonstrates coherent and ultrastrong coupling between a few-electron quantum dot and a terahertz resonator, revealing hybrid light-matter excitations in a solid-state system.

Contribution

It reports the first observation of ultrastrong coupling involving a quantum dot with only a few electrons and a terahertz resonator.

Findings

Quantum dot shows current spectrum indicating coherent coupling with the resonator.

Coupling between the 2DES and the resonator reaches the ultrastrong regime.

Coupling between the quantum dot and the resonator is near the ultrastrong regime despite few electrons.

Abstract

We have investigated light-matter hybrid excitations in a quantum dot (QD)-terahertz (THz) optical resonator coupled system. We fabricate a gate-defined QD in the vicinity of a THz split-ring resonator (SRR) by using a AlGaAs/GaAs two-dimensional electron system (2DES). By illuminating the system with THz radiation, the QD shows a current change whose spectrum exhibits coherent coupling between the electrons in the QD and the SRR as well as coupling between the 2DES and the SRR. The latter coupling enters the ultrastrong coupling regime and the coupling between the QD and the SRR is also very close to the ultrastrong coupling regime, despite the fact that only a few electrons reside in the QD.