Физика низких температур, 2017, № 01

Особенности магнитострикции металлов при электронных топологических переходах

2017-01-01T00:00:00Z

Особенности магнитострикции металлов при электронных топологических переходах Микитик, Г.П.; Шарлай, Ю.В. Исследованы особенности магнитострикции металлов в условиях близости уровня химического потенциала электронов к критической энергии электронного энергетического спектра, при которой происходит электронный топологический переход 2½ или 3½ рода. Показано, что экспериментальное исследование магнитострикции может быть эффективным средством детектирования этих переходов в металлах.; Досліджено особливості магнітострикції металів в умовах близькості рівня хімічного потенціалу електронів до критичної енергії електронного енергетичного спектра, при якій відбувається електронний топологічний перехід 2½ або 3½ роду. Показано, що експериментальне дослідження магнітострикції може бути ефективним засобом детектування цих переходів в металах.; The properties of magnetostriction in metals are studied in cases when the chemical potential of electrons is close to the critical energy of the electron energy spectrum, at which there is an electron topological transition of 2½ or 3½ kind. It is shown that the experimental study of magnetostriction can be an effective method for detecting these transitions in metals.

The excitation and detection of a leaky surface electromagnetic wave on a high-index dielectric grating in a prism-coupler geometry

2017-01-01T00:00:00Z

The excitation and detection of a leaky surface electromagnetic wave on a high-index dielectric grating in a prism-coupler geometry Simonsen, I.; Maradudin, A.A. A periodically corrugated interface between vacuum and a high-index dielectric medium supports a p-polarized leaky surface electromagnetic wave whose sagittal plane is perpendicular to the generators of the interface. This wave is bound to the surface in the vacuum region, but radiates into the high-index dielectric medium. We study the excitation of this wave by p-polarized light incident from a prism on whose planar base the highindex dielectric medium in the form of a film is bonded. The unilluminated surface of the film is periodically corrugated, and is in contact with vacuum. Peaks and dips in the dependence of several low-order diffraction efficiencies on the angle of incidence (Wood anomalies) are the signatures of the excitation of the surface wave.

Enhancement of Raman scattering from molecules placed near metal nanoparticles

2017-01-01T00:00:00Z

Enhancement of Raman scattering from molecules placed near metal nanoparticles Barbiellini, B. Large Raman scattering cross sections from molecules on surfaces of metallic nanoparticles are described within a renormalization-group theory. In this approach the valence electrons of the molecules are embedded in an effective medium described by a dielectric function, which integrates out the effect of the plasmonic excitations of the metallic nanoparticles. The source of the enhanced photon inelastic scattering is produced by the resonant excitation of surface plasmons at the metallic nanoparticles. A similar theory has been successfully used to explain the resonant x-ray inelastic scattering and the behavior of nonlinear susceptibilities at the x-ray edges.

Long-lived magnetoexcitons in 2D-fermion system

2017-01-01T00:00:00Z

Long-lived magnetoexcitons in 2D-fermion system Kulik, L.V.; Zhuravlev, A.S.; Gorbunov, A.V.; Timofeev, V.B.; Kukushkin, I.V. The paper addresses the experimental technique that, when applied to a 2D-electron system in the integer quantum Hall regime with filling factor ν = 2 (the Hall insulating state), allows resonant excitation of magnetoexcitons, their detection, control of an ensemble of long-lived triplet excitons and investigation of their radiationless decay related to exciton spin relaxation into the ground state. The technique proposed enables independent control of photoexcited electrons and Fermi-holes using photoinduced resonance reflection spectra as well as estimate with a reasonable degree of accuracy the resulting density of photoinduced electron-hole pairs bound into magnetoexcitons. The mere existence of triplet excitons was directly established by inelastic light scattering spectra which were analyzed to determine the value of singlet-triplet exciton splitting. It was found that the lifetimes of triplet excitons conditioned by electron spin relaxation in highly perfect GaAs/AlGaAs heterostructures with highly mobile 2D electrons are extremely long exceeding 100 μs at T < 1 K. The paper presents a qualitative explanation of the long-spin relaxation lifetimes which are unprecedented for translation-invariant 2D systems. This enabled us to create sufficiently high concentrations of triplet magnetoexcitons, electrically neutral excitations following Bose–Einstein statistics, in a Fermi electron system and investigate their collective properties. At sufficiently high densities of triplet magnetoexcitons and low temperatures, T < 1 K, the degenerate magnetofermionic system exhibits condensation of the triplet magnetoexcitons into a qualitatively new collective state with unusual properties which occurs in the space of generalized moments (magnetic translation vectors). The occurrence of a condensed phase is accompanied with a significant decrease in the viscosity of the photoexcited system, which is responsible for electron spin transport at macroscopic distances, as well as with the effects of threshold enhancement of the system response to the external action of the electromagnetic field and emergence of a new intensive radiative recombination channel.