Lande g factors and orbital momentum quenching in semiconductor quantum dots

We report a large g-factor tunability of a single hole spin in an InGaAs quantum dot via an electric field. The magnetic field lies in the in-plane direction x, the direction required for a coherent hole spin. The electrical field lies along the growth direction z and is changed over a large range, 100 kV/cm. Both electron and hole g-factors are determined by high resolution laser spectroscopy with resonance fluorescence detection. This, along with the low electrical-noise en...

We present a magneto-photoluminescence study on neutral and charged excitons confined to InAs/GaAs quantum dots. Our investigation relies on a confocal microscope that allows arbitrary tuning of the angle between the applied magnetic field and the sample growth axis. First, from experiments on neutral excitons and trions, we extract the in-plane and on-axis components of the Land\'e tensor for electrons and holes in the s-shell. Then, based on the doubly negatively charged ex...

We report on the theoretical study of the hole states in II-IV quantum dots of a spherical and ellipsoidal shape, described by a smooth potential confinement profiles, that can be modelled by a Gaussian functions in all three dimensions. The universal dependencies of the hole energy, $g$-factor and localization length on a quantum dot barrier height, as well as the ratio of effective masses of the light and heavy holes are presented for the spherical quantum dots. The splitti...

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 di...

We present a detailed investigation of different excitonic states weakly confined in single GaAs/AlGaAs quantum dots obtained by the Al droplet-etching method. For our analysis we make use of temperature-, polarization- and magnetic field-dependent $\mu$-photoluminescence measurements, which allow us to identify different excited states of the quantum dot system. Besides that, we present a comprehensive analysis of g-factors and diamagnetic coefficients of charged and neutral...

We investigate transport properties of stable gate-defined quantum dots formed in an InSb$_{0.87}$As$_{0.13}$ quantum well. High $\textit{g}$-factor and strong spin-orbit-coupling make InSb$_x$As$_{1-x}$ a promising platform for exploration of topological superconductivity and spin-based devices. We extract a nearly isotropic in-plane effective $\textit{g}$-factor by studying the evolution of Coulomb blockade peaks and differential conductance as a function of the magnitude a...

We analyze orbital effects of an in-plane magnetic field on the spin structure of states of a gated quantum dot based in a two-dimensional electron gas. Starting with a $k \cdot p$ Hamiltonian, we perturbatively calculate these effects for the conduction band of GaAs, up to the third power of the magnetic field. We quantify several corrections to the g-tensor and reveal their relative importance. We find that for typical parameters, the Rashba spin-orbit term and the isotropi...

We study the quantum-confined Stark effect in single InAs/GaAs quantum dots embedded within a AlGaAs/GaAs/AlGaAs quantum well. By significantly increasing the barrier height we can observe emission from a dot at electric fields of -500 kV/cm, leading to Stark shifts of up to 25 meV. Our results suggest this technique may enable future applications that require self-assembled dots with transitions at the same energy.

The emission spectral pattern of a charged exciton in a semiconductor quantum dot is composed of a quadruplet of linearly polarized lines in the presence of a magnetic field oriented perpendicularly to the direction of the photon momentum. By measuring the Zeeman splittings, we obtain the effective g factors of the carriers and find that the hole g factor is very sensitive to the QD shape asymmetry. By comparing the effective g factors obtained for the neutral and the charged...

The electron and hole g factors are the key quantities for the spin manipulations in semiconductor quantum nanostructures. However, for the individual nanostructures, the separate determination including the signs of those g factors is difficult by using some methods adopted conventionally in bulks and quantum wells. We report a convenient optical method for the sign identification of out-of-plane g factors in the individual quantum nanostructures, which utilizes the opticall...