Sub-Kelvin optical thermometry of an electron reservoir coupled to a self-assembled InGaAs quantum dot

TL;DR

This paper introduces a method using resonant laser spectroscopy of quantum dots to measure the temperature of an electron reservoir at sub-Kelvin temperatures, revealing insights into electron thermalization.

Contribution

It presents a novel optical thermometry technique for electron reservoirs near quantum dots, effective in the sub-Kelvin temperature range.

Findings

Successfully measured electron reservoir temperature below 1 Kelvin.

Demonstrated thermalization of quantum dot electrons with the reservoir.

Established optical thermometry as a sensitive tool at ultra-low temperatures.

Abstract

We show how resonant laser spectroscopy of the trion optical transitions in a self-assembled quantum dot can be used to determine the temperature of a nearby electron reservoir. At finite magnetic field the spin-state occupation of the Zeeman-split quantum dot electron ground states is governed by thermalization with the electron reservoir via co-tunneling. With resonant spectroscopy of the corresponding excited trion states we map out the spin occupation as a function of magnetic field to establish optical thermometry for the electron reservoir. We demonstrate the implementation of the technique in the sub-Kelvin temperature range where it is most sensitive, and where the electron temperature is not necessarily given by the cryostat base temperature.