Spin noise spectroscopy of a single quantum well microcavity

Abstract

We report on the first experimental observation of spin noise in a single semiconductor quantum well embedded into a microcavity. The great cavity-enhanced sensitivity to fluctuations of optical anisotropy has allowed us to measure the Kerr rotation and ellipticity noise spectra in the strong coupling regime. The spin noise spectra clearly show two resonant features: a conventional magneto-resonant component shifting towards higher frequencies with magnetic field and an unusual "nonmagnetic" component centered at zero frequency and getting suppressed with increasing magnetic field. We attribute the first of them to the Larmor precession of free electron spins, while the second one being presumably due to hyperfine electron-nuclei spin interactions.Introduction. In the present-day physics of semiconductor nanostructures, a considerable interest is shown for the fundamental spin-related properties which are also promising in applications. Among optical methods of spin dynamics studies, an important place is given to the Faraday-rotation-based spin noise spectroscopy (SNS) which became well-known and popular during the last several years [1]. The advantages of SNS are primarily owed to its nonperturbative nature because probing the sample response by a weak laser beam in the region of transparency does not lead to any real electronic transitions. Extreme smallness of the magnetization fluctuations detected with the SNS technique calls for the highest polarimetric sensitivity which is achieved by using various electronic or optical means. A real breakthrough occurred when the fast-Fourier-transform (FFT) spectrum analyzers were applied in electronics of the SNS technique [2]. The most straightforward optical way to enhance the polarimetric sensitivity implies increasing intensity of the probe light beam and, simultaneously, leaving the input power of photodetector on the admissible level. This can be implemented either by using highextinction polarization geometries [3] or by placing the sample inside a high-Q optical cavity [4]. In both cases, the light power density on the sample can be increased by a few orders of magnitude, with the light power on the photodetector and, therefore, the photocurrent shot noise remaining on the same low level.For low-dimensional semiconductor structures (quantum wells, wires and dots) the problem of polarimetric sensitivity is especially topical. In Ref.[5], in order to increase the signal, the spin noise spectra of n-doped GaAs quantum wells were studied in the samples containing ten identical quantum wells (QWs). The measurement of the spin noise spectrum of a layer of InAs/GaAs quantum dots (QDs) in a high-finesse microcavity allowed Dahbashi et al. [6] to perform unique investigation of spin dynamics of a single heavy hole localized in a selected QD. We are not aware of any experimental study of spin

Exciton spin noise in quantum wells

“…For the probe beam polarized along x-axis the small fluctuations of Faraday and ellipticity angles δθ F and δθ E are given by 8,40,45 …”

“…By now it has already been successfully applied to bulk semiconductors, 5,6 multiple and single quantum well structures, 7,8 individual quantum dots and quantum dot ensembles [9][10][11] making it possible to reveal and analyze spin dynamics of electrons and holes.…”

“…use of high-extinction polarization geometries and/or placing the sample into the optical cavity are applied. 8,15 In this regard, the spin noise spectra of excitons can be especially interesting because these particles do not exist without pumping, while their spin dynamics is quite rich, particularly, owing to an interplay of optically active and inactive states, see e.g. Refs.…”

Spinor stochastic resonance

“…In this framework, noise inherently impacts the overall dynamics of systems and should be studied thoroughly. Recently, intensity noise measurements in polariton gas have been reported both on theoretical [20] and experimental aspects * hadis.abbaspour@epfl.ch [21,22], with particularly the demonstration of the stochastic resonance in the polariton population [5]. More than just an intriguing phenomenon, stochastic resonance might be used as a tool to increase the sensitivity of nonlinear devices and to extract signal information from a noisy environment [23].…”

Probing many-body localization by spin noise spectroscopy

“…Intrinsic spin fluctuations of electrons and holes are passively detected in SNS by measuring optical Faraday rotation fluctuations of a linearly polarized probe laser beam passing through the sample [27][28][29][30][31][32][33][34][35][36][37][38]. SNS with a single probe laser has been useful in characterizing various properties (e.g., g-factors, relaxation rates and decoherence times) of different spin ensembles, such as specific alkali atoms [30], itinerant electron spins in semiconductors [33] and localized hole spins in quantum dot ensembles [34].…”