Physics-Uspekhi

This review is devoted to studies of quantum optics effects for quantum emitters (QEs) in the near field of nanoparticles (NPs). In the simple model of a two-level QE located near a plasmon NP, we analyze the mechanisms for modifying the radiative and nonradiative decay rates and discuss the distribution of the near-field intensity and polarization around the NP. This distribution has a complex structure, being significantly dependent on the polarization of the external radiation field and on the parameters of NP plasmon resonances. The quantum optics effects in the system (NP + QE + external laser field) are analyzed, including the near-field modification of the resonance fluorescence spectrum of a QE, the bunching/antibunching effects and photon quantum statistics effects in the spectrum, the formation of squeezed light states, and quantum entangled states in such systems.

We review the most significant results obtained in the framework of the microscopic approach to a systematic study of magnetic dynamics in two-dimensional ferromagnetic and antiferromagnetic materials with a strong Rashba spin-orbit coupling. For model systems, we discuss the microscopic derivation of the Gilbert damping tensor, spin-orbit and spin-transfer torques, and symmetric and antisymmetric exchange interactions. It is shown that in both antiferromagnetic and ferromagnetic systems, the presence of a sufficiently strong spin-orbit coupling leads to an anisotropy of spin torques and Gilbert damping. We focus on an analysis of spin-orbit torques in a two-dimensional Rashba antiferromagnet. We also address the possibility of switching the antiferromagnetic order parameter via short current pulses in the plane of the sample.

This review describes the current state of research on the formation of a nanocrystalline structure in amorphous alloys under thermal and deformation effects. The processes of formation of nanocrystals in homogeneous and heterogeneous amorphous structures (nanoglass) are considered. Changes in the magnetic and mechanical properties during the formation of a composite amorphous-nanocrystalline structure with different structural parameters are analyzed. The possibility of amorphous phase rejuvenation from a partially crystalline structure under cryogenic thermocycling treatment is shown.

The main issues and areas of application of photothermal and optoacoustic spectroscopy are reviewed. Progress in innovative techniques in the most actively developing areas is presented, including microspectroscopy, multispectral techniques, the measurements of single particles and objects with a resolution better than the diffraction limit (nanoscopy) by both optical and probe-based methods. Possible applications of photothermal and optoacoustic spectroscopy for determining the properties of materials, studying photochemistry and fluorescence, chemical reactions, and analytical and applied chemistry, and solving biomedical problems is discussed. Some prospects for the development of these methods are presented.

This review is devoted to studies of quantum optics effects for quantum emitters (QEs) in the near field of nanoparticles (NPs). In the simple model of a two-level QE located near a plasmon NP, we analyze the mechanisms for modifying the radiative and nonradiative decay rates and discuss the distribution of the near-field intensity and polarization around the NP. This distribution has a complex structure, being significantly dependent on the polarization of the external radiation field and on the parameters of NP plasmon resonances. The quantum optics effects in the system (NP + QE + external laser field) are analyzed, including the near-field modification of the resonance fluorescence spectrum of a QE, the bunching/antibunching effects and photon quantum statistics effects in the spectrum, the formation of squeezed light states, and quantum entangled states in such systems.

We review the most significant results obtained in the framework of the microscopic approach to a systematic study of magnetic dynamics in two-dimensional ferromagnetic and antiferromagnetic materials with a strong Rashba spin-orbit coupling. For model systems, we discuss the microscopic derivation of the Gilbert damping tensor, spin-orbit and spin-transfer torques, and symmetric and antisymmetric exchange interactions. It is shown that in both antiferromagnetic and ferromagnetic systems, the presence of a sufficiently strong spin-orbit coupling leads to an anisotropy of spin torques and Gilbert damping. We focus on an analysis of spin-orbit torques in a two-dimensional Rashba antiferromagnet. We also address the possibility of switching the antiferromagnetic order parameter via short current pulses in the plane of the sample.

This review describes the current state of research on the formation of a nanocrystalline structure in amorphous alloys under thermal and deformation effects. The processes of formation of nanocrystals in homogeneous and heterogeneous amorphous structures (nanoglass) are considered. Changes in the magnetic and mechanical properties during the formation of a composite amorphous-nanocrystalline structure with different structural parameters are analyzed. The possibility of amorphous phase rejuvenation from a partially crystalline structure under cryogenic thermocycling treatment is shown.

This review is devoted to a discussion of new (and often unexpected) aspects of the old problem of elastic light scattering by small metal particles, whose size is comparable to or smaller than the thickness of the skin layer. The main focus is on elucidating the physical grounds for these new aspects. It is shown that, in many practically important cases, the scattering of light by such particles, despite their smallness, may have almost nothing in common with the Rayleigh scattering. So-called anomalous scattering and absorption, as well as Fano resonances, including unconventional (associated with the excitation of longitudinal electromagnetic oscillations) and directional Fano resonances, observed only at a small solid angle, are discussed in detail. The review contains a Mathematical Supplement, which includes a summary of the main results of the Mie theory and a discussion of some general properties of scattering coefficients. In addition to being of purely academic interest, the phenomena considered in this review can find wide applications in biology, medicine, pharmacology, genetic engineering, imaging of ultra-small objects, ultra-high-resolution spectroscopy, information transmission, recording, and processing, as well as many other applications and technologies.

We discuss the properties of topologically nontrivial superconducting phases and the conditions for their realization in condensed matter, the criteria for the appearance of elementary Majorana-type excitations in solids, and the corresponding principles and experimental methods for identifying Majorana bound states (MBSs). Along with the well-known Kitaev chain and superconducting nanowire (SW) models with spin–orbit coupling in an external magnetic field, we discuss models of quasi-two-dimensional materials in which MBSs are realized in the presence of noncollinear spin ordering. For finite-length SWs, we demonstrate a cascade of quantum transitions occurring with a change in the magnetic field, accompanied by a change in the fermion parity of the ground state. The corresponding anomalous behavior of the magnetocaloric effect can be used as a tool for identifying MBSs. We devote considerable attention to the analysis of the transport characteristics of devices that contain topologically nontrivial materials. The results of studying the conductance of an Aharonov–Bohm ring whose arms are connected by an SW are discussed in detail. An important feature of this device is the appearance of Fano resonances in the dependence of conductance on the magnetic field when the SW is in a topologically nontrivial phase. We establish a relation between the characteristics of such resonances and the spatial structure of the lowest-energy SW state. The conditions for the occurrence of an MBS in the phase of the coexistence of chiral d + id superconductivity and 120-degree spin ordering are determined in the framework of the t – J – V model on a triangular lattice. We take electron–electron interactions into account in discussing the topological invariants of low-dimensional superconducting materials with noncollinear spin ordering. The formation of Majorana modes in regions with an odd value of a topological invariant is demonstrated. The spatial structure of these excitations in the Hubbard fermion ensemble is determined.