Spin noise of electrons and holes in self-assembled quantum dots

TL;DR

This study measures and analyzes the spin noise spectra of electrons and holes in quantum dots, revealing their g-factors, dephasing rates, and anisotropic properties using advanced optical magnetometry.

Contribution

It introduces a sensitive optical Faraday rotation spectrometer for real-time, high-resolution spin noise measurements in quantum dots, uncovering energy-dependent g-factor anisotropy.

Findings

Distinct electron and hole spin noise peaks identified.

Magnetic field shifts reveal g-factors and dephasing rates.

Energy-dependent in-plane hole g-factor anisotropy observed.

Abstract

We measure the frequency spectra of random spin fluctuations, or "spin noise", in ensembles of (In,Ga)As/GaAs quantum dots (QDs) at low temperatures. We employ a spin noise spectrometer based on a sensitive optical Faraday rotation magnetometer that is coupled to a digitizer and field-programmable gate array, to measure and average noise spectra from 0-1 GHz continuously in real time with sub-nanoradian/root-Hz sensitivity. Both electron and hole spin fluctuations generate distinct noise peaks, whose shift and broadening with magnetic field directly reveal their g-factors and dephasing rates within the ensemble. A large, energy-dependent anisotropy of the in-plane hole g-factor is clearly exposed, reflecting systematic variations in the average QD confinement potential.