Ultimate photo-induced Kerr rotation achieved in semiconductor microcavities

Photoinduced Kerr rotation by more than $\pi /2$ radians is demonstrated in planar quantum well microcavity in the strong coupling regime. This result is close to the predicted theoretical maximum of $\pi$. It is achieved by engineering microcavity parameters such that the optical impedance matching condition is reached at the smallest negative detuning between exciton resonance and the cavity mode. This ensures the optimum combination of the exciton induced optical non-linearity and the enhancement of the Kerr angle by the cavity. Comprehensive analysis of the polarization state of the light in this regime shows that both renormalization of the exciton energy and the saturation of the excitonic resonance contribute to the observed optical nonlinearities.Comment: Shortened version prepared to submit in Phys. Rev. Letter

Ballistic spin transport in exciton gases

Traditional spintronics relies on spin transport by charge carriers, such as electrons in semiconductor crystals. This brings several complications: the Pauli principle prevents the carriers from moving with the same speed; Coulomb repulsion leads to rapid dephasing of electron flows. Spin-optronics is a valuable alternative to traditional spintronics. In spin-optronic devices the spin currents are carried by electrically neutral bosonic quasi-particles: excitons or exciton-polaritons. They can form highly coherent quantum liquids and carry spins over macroscopic distances. The price to pay is a finite life-time of the bosonic spin carriers. We present the theory of exciton ballistic spin transport which may be applied to a range of systems where bosonic spin transport has been reported, in particular, to indirect excitons in coupled GaAs/AlGaAs quantum wells. We describe the effect of spin-orbit interaction of electrons and holes on the exciton spin, account for the Zeeman effect induced by external magnetic fields, long range and short range exchange splittings of the exciton resonances. We also consider exciton transport in the non-linear regime and discuss the definitions of exciton spin current, polarization current and spin conductivity.Comment: 16 pages, 10 figures to be published in Phys. Rev.

Simultaneous measurements of nuclear spin heat capacity, temperature and relaxation in GaAs microstructures

Heat capacity of the nuclear spin system (NSS) in GaAs-based microstructures has been shown to be much greater than expected from dipolar coupling between nuclei, thus limiting the efficiency of NSS cooling by adiabatic demagnetization. It was suggested that quadrupole interaction induced by some small residual strain could provide this additional reservoir for the heat storage. We check and validate this hypothesis by combining nuclear spin relaxation measurements with adiabatic remagnetization and nuclear magnetic resonance experiments, using electron spin noise spectroscopy as a unique tool for detection of nuclear magnetization. Our results confirm and quantify the role of the quadrupole splitting in the heat storage within NSS and provide additional insight into fundamental, but still actively debated relation between a mechanical strain and the resulting electric field gradients in GaAs.Comment: 11 pages, 4 figures, 1 tabl

Assessment of News Items Objectivity in Mass Media of Countries with Intelligence Systems: the Brexit Case

The role of mass media in society keeps the problem of manipulative influence distinction and the contiguous phenomena, chief among which is objectivity and authenticity of news items, current. The research provides a detailed study of the information broadcasting mechanisms in the media area, defines the problems, impeding an impersonal reproduction and disclosure of information, clarifies the verification methods, and gives their topology. In this research, we examined how the mass media of different countries presented the same event to the public. The publications of four mass media, concerning such an event as the withdrawal of the United Kingdom from the European Union (Brexit), have been determined as an object of the analysis. The chosen mass media refer to the countries, which are not the direct participants of that process: Russia, the USA, and Ukraine. D. Brewer’s criteria were used to define the objectivity of the news items. A relative sentiment of the news, which became the objective analysis basis, has been identified using linguistic rate with Eureka Engine intelligence system. The obtained results predominantly confirmed the hypothesis, that the mass media of different countries would represent the process of the UK withdrawal from the EU according to the country’s policy and interpret the facts in their favor. All the four mass media demonstrate the partiality when broadcasting the current situation in the matter of Brexit. The concepts being the semantic kernel elements of mass media publications have emotional coloring. The sentiment analysis of the publications resulted in the conclusion that only one of the four mass media gave a neutral assessment of the Brexit situation. The other three held to the political stance of their edition or government. The research results indicate that the problem of mass media objectivity remains relevant. The correctional impact on public opinion through mass media is extremely high. Therefore, forming the personal attitude toward the situation or event should occur with using several verifications methods and mass media sources at once

Spin Texture in a Cold Exciton Gas

We report on the observation of a spin texture in a cold exciton gas in a GaAs/AlGaAs coupled quantum well structure. The spin texture is observed around the exciton rings. The observed phenomena include: a ring of linear polarization, a vortex of linear polarization with polarization perpendicular to the radial direction, an anisotropy in the exciton flux, a skew of the exciton fluxes in orthogonal circular polarizations and a corresponding four-leaf pattern of circular polarization, a periodic spin texture, and extended exciton coherence in the region of the polarization vortex. The data indicate a transport regime where the spin polarization is locked to the direction of particle propagation and scattering is suppressed.Comment: version 2 contains updated supplementary materia

Synthesis and magnetic properties of BiFe1-xCoxO3 (x = 0-0.07)

This research was carried out under the financial support of the Russian Foundation for Basic Research №17-08-00893

Self-assembly of hollow bismuth ferrite spheres

This research was carried out under the financial support of the Russian Foundation for Basic Research №17-08-00893