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

The spin fluctuations of electron and hole doped self-assembled quantum dot ensembles are measured optically in the low-intensity limit of a probe laser in absence and presence of longitudinal or transverse static magnetic fields. The experimental results are modeled by two complementary approaches based either on semiclassical or quantum mechanical descriptions. This allows us to characterize the hyperfine interaction of electron and hole spins with the surrounding bath of nuclei on time scales covering several orders of magnitude. Our results demonstrate (i) the intrinsic precession of the electron spin fluctuations around the effective nuclear Overhauser field caused by the host lattice nuclear spins, (ii) the comparably long time scales for electron and hole spin decoherence, as well as (iii) the dramatic enhancement of the spin lifetimes induced by a longitudinal magnetic field due to the decoupling of nuclear and charge carrier spins.

The spin inertia measurement is a recently emerged tool to study slow spin dynamics, which is based on the excitation of the system by a train of circularly polarized pulses with alternating helicity. Motivated by the experimental results reported in E. A. Zhukov et al., arXiv:1806.11100 we develop the general theory of spin inertia of localized charge carriers. We demonstrate that the spin inertia measurement in longitudinal magnetic field allows one to determine the parameters of the spin dynamics of resident charge carriers and of photoexcited trions, such as the spin relaxation times, longitudinal g-factors, parameters of hyperfine interaction and nuclear spin correlation times. arXiv:1806.11098v2 [cond-mat.mes-hall]

Rapid development of spin noise spectroscopy of the last decade has led to a number of remarkable achievements in the fields of both magnetic resonance and optical spectroscopy. In this report, we demonstrate a new – magnetometric – potential of the spin noise spectroscopy and use it to study magnetic fields acting upon electron spin-system of an n-GaAs layer in a high-Q microcavity probed by elliptically polarized light. Along with the external magnetic field, applied to the sample, the spin noise spectrum revealed the Overhauser field created by optically oriented nuclei and an additional, previously unobserved, field arising in the presence of circularly polarized light. This “optical field” is directed along the light propagation axis, with its sign determined by sign of the light helicity. We show that this field results from the optical Stark effect in the field of the elliptically polarized light. This conclusion is supported by theoretical estimates.

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We report on the observation of photoluminescence (PL) with a narrow 18 meV peak width from molecular beam epitaxy grown MoS 2 on graphene/Ir(111). This observation is explained in terms of a weak graphene-MoS 2 interaction that prevents PL quenching expected for a metallic substrate. The weak interaction of MoS 2 with the graphene is highlighted by angle-resolved photoemission spectroscopy and temperature dependent Raman spectroscopy. These methods reveal that there is no hybridization between electronic states of graphene and MoS 2 and a different thermal expansion of graphene and MoS 2 . Molecular beam epitaxy grown MoS 2 on graphene is therefore an important platform for optoelectronics which allows for large area growth with controlled properties. arXiv:1809.01886v1 [cond-mat.mes-hall] 6 Sep 2018 Narrow photoluminescence peak of epitaxial MoS 2 on graphene/Ir (111)

The spin dynamics in a broad range of systems can be studied using circularly polarized optical excitation with alternating helicity. The dependence of spin polarization on the frequency of helicity alternation, known as the spin inertia effect, is used here to study the spin dynamics in singly-charged (In,Ga)As/GaAs quantum dots (QDs) providing insight into spin generation and accumulation processes. We demonstrate that the dependence of spin polarization in n-and p-type QDs on the external magnetic field has a characteristic V-and M-like shape, respectively. This difference is related to different microscopic mechanisms of resident carriers spin orientation. It allows us to determine the parameters of the spin dynamics both for the ground and excited states of singlycharged QDs.

In this paper a microscopic theory of spin fluctuations in an ensemble of electrons localized on donors in a bulk semiconductor has been developed. Both the hyperfine interaction of the electron spin with spins of lattice nuclei and the exchange interaction between the electrons have been taken into account. We propose a model of clusters to calculate spin noise spectra of the ensemble of localized charge carriers. It has been shown that the electron-electron exchange interaction leads to an effective averaging of random nuclear fields and a shift of the peak in the spin-fluctuation spectrum towards lower frequencies.