Spin Noise of Electrons and Holes in Self-Assembled Quantum Dots

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 subnanoradian/sqrt[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.

Measurement of heavy-hole spin dephasing in (InGa)As quantum dots

“…Spin noise spectroscopy has been used on QD ensembles once before, however, mainly to study the anisotropy of the heavy-hole g-factor. 9 In the following, we apply magnetic fields at oblique angle with respect to the projection direction (z) of our all optical spin sensitive probing technique. The effective magnetic field given by the superposition of the stochastic nuclear and the applied external magnetic field divides the spin dynamics into a longitudinal and transverse component.…”

Multidimensional characterization of stochastic dynamical systems based on multiple perturbations and measurements

“…These measure both response and spontaneous fluctuations and are not causal. In the linear regime, there are two possible signals (excitation followed by measurement or two measurements) but they are connected by the fluctuation dissipation (FD) [2][3][4] relation and carry the same information. 5 This is not the case for the nonlinear response since there is no universal FD theorem.…”

Spin noise spectroscopy of quantum dot molecules

“…In this work, we explore the potential of an alternative approach, called the spin noise spectroscopy (SNS) that has already been demonstrated as a powerful probe of physics of hole or electron spins localized in separated QDs 11,12 . In this approach, the spin noise power spectrum is obtained by measuring the fluctuations of the optical Faraday rotation of a linearly polarized beam passing through a region with spins.…”