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## Optical manifestation of the Stoner ferromagnetic transition in two-dimensional electron systems

We perform a magneto-optical study of a two-dimensional electron systems in the regime of the Stoner

ferromagnetic instability for even quantum Hall filling factors on MgxZn1−xO/ZnO heterostructures. Under

conditions of Landau-level crossing, caused by enhanced spin susceptibility in combination with the tilting of the

magnetic field, the transition between two rivaling phases, paramagnetic and ferromagnetic, is traced in terms of

optical spectra reconstruction. Synchronous sharp transformations are observed both in the photoluminescence

structure and parameters of collective excitations upon transition from paramagnetic to ferromagnetic ordering.

Based on these measurements, a phase diagram is constructed in terms of the two-dimensional electron density

and tilt angle of the magnetic field.Apart from stable paramagnetic and ferromagnetic phases, an instability region

is found at intermediate parameters with the Stoner transition occurring at ν ≈ 2. The spin configuration in all

cases is unambiguously determined by means of inelastic light scattering by spin-sensitive collective excitations.

One indicator of the spin ordering is the intra-Landau-level spin exciton, which acquires a large spectral weight

in the ferromagnetic phases. The other is an abrupt energy shift of the intersubband charge density excitation due

to reconstruction of the many-particle energy contribution. From our analysis of photoluminescence and light

scattering data, we estimate the ratio of surface areas occupied by the domains of the two phases in the vicinity

of a transition point. In addition, the thermal smearing of a phase transition is characterized.

The conference is devoted to fundamental problems of semiconductor physics.Main sections of the program: 1. Bulk semiconductors: electrical and optical properties, relaxation of charge carriers, ultrafast phenomena, excitons, phonons, phase transitions, ordering. 2. Surface, films, layers: epitaxy, atomic and electronic structure of the surface, adsorption and surface reactions, processes of formation (self-organization) of nanoclusters, STM and AFM, optical microscopy of the near field. 3. Heterostructures, superlattices, one-dimensional systems: structural and optical properties, electronic transport. 4. Two-dimensional systems: structural, electronic, magnetic and optical properties, tunneling, localization, phonons, plasmons, quantum Hall effect, correlation effects. 5. Zero-dimensional systems (quantum dots, nanocrystals): energy spectrum, optical properties, tunnel transport. 6. Spin phenomena, spintronics, nanomagnetism. 7. Impurities and defects (bulk semiconductors and quantum-dimensional structures): impurities with shallow and deep levels, magnetic impurities, structural defects, disordered semiconductors. 8. High-frequency phenomena in semiconductors (microwave and terahertz range). 9. Carbon and graphene-like nanomaterials, transition metal dichalcogenide monolayers, perovskites, organic semiconductors, molecular systems. 10. Photonic crystals, microresonators and metamaterials. Nanophotonics. 11. Semiconductor devices: technology, research methods, and nanodevices. 12. Nano-and optomechanics. 13. Topological insulators and Weyl semimetals.Выделите текст, чтобы посмотреть примерыДелитесь своими подборкамиСоздавайте подборки переводов для учёбы, работы или просто так и используйте вместе с друзьямиПопробоватьПримерыУстановите приложение на смартфон и работайте офлайн+Установить ПереводчикСообщение отправленоОтправить ещё разПереводите в Яндекс.Браузере

The photoemission of free charge carriers into high-ohmic semiconductor created by light illumination of near-contact-area of ohmic contacts to cadmium telluride sample was investigated. It was revealed, that near-contact-area light illumination influences both on contact transition resistance and on volume conductivity of the crystal due to increasing of main charge carrier concentration. The method of separate determination of contact transition and sample volume resistances, suitable for high-ohmic semiconductors, was suggested.

Physics of many-body systems where particles are restricted to move in two spatial dimensions is challenging and even controversial: On one hand, neither long-range order nor Bose condensation may appear in innite uniform 2D systems at nite temperature, on the other hand this does not prohibit super uidity or superconductivity. Moreover, 2D superconductors, such as cuprates, are among the systems with highest critical temperatures. Ultracold atoms are a platform for studying 2D physics. Uniquely to other physical systems, quantum statistics may be completely changed in an ultracold gas: an atomic Fermi gas may be smoothly crossed over into a gas of Bose molecules (or dimers) by tuning interatomic interactions. We review recent experiments where such crossover has been demonstrated as well as critical phenomena in the Fermi-to-Bose crossover. We also present simple theoretical models describing the gas at different points of the crossover and compare the data to these and more advanced models.

For the Dirac 2D-operator in a constant magnetic field with perturbing electric potential, we derive Hamiltonians describing the quantum quasiparticles (Larmor vortices) at Landau levels. The discrete spectrum of this Hall-effect quantum Hamiltonian can be computed to all orders of the semiclassical approximation by a deformed Planck-type quantization condition on the 2D-plane; the standard magnetic (symplectic) form on the plane is corrected by an “electric curvature” determined via derivatives of the electric field. The electric curvature does not depend on the magnitude of the electric field and vanishes for homogeneous fields (i.e., for the canonical Hall effect). This curvature can be treated as an effective magnetic charge of the inhomogeneous Hall 2D-nanosystem.

The dynamics of a two-component Davydov-Scott (DS) soliton with a small mismatch of the initial location or velocity of the high-frequency (HF) component was investigated within the framework of the Zakharov-type system of two coupled equations for the HF and low-frequency (LF) fields. In this system, the HF field is described by the linear Schrödinger equation with the potential generated by the LF component varying in time and space. The LF component in this system is described by the Korteweg-de Vries equation with a term of quadratic influence of the HF field on the LF field. The frequency of the DS soliton`s component oscillation was found analytically using the balance equation. The perturbed DS soliton was shown to be stable. The analytical results were confirmed by numerical simulations.

Radiation conditions are described for various space regions, radiation-induced effects in spacecraft materials and equipment components are considered and information on theoretical, computational, and experimental methods for studying radiation effects are presented. The peculiarities of radiation effects on nanostructures and some problems related to modeling and radiation testing of such structures are considered.

This volume presents new results in the study and optimization of information transmission models in telecommunication networks using different approaches, mainly based on theiries of queueing systems and queueing networks .

The paper provides a number of proposed draft operational guidelines for technology measurement and includes a number of tentative technology definitions to be used for statistical purposes, principles for identification and classification of potentially growing technology areas, suggestions on the survey strategies and indicators. These are the key components of an internationally harmonized framework for collecting and interpreting technology data that would need to be further developed through a broader consultation process. A summary of definitions of technology already available in OECD manuals and the stocktaking results are provided in the Annex section.