Vol 166, No 1 (2024)

To the 130th anniversary of Pyotr Leonidovich Kapitsa

Excitons in van der Waals heterostructures based on atomically thin transition metal dichalco-genides  are  considered  as  potential  candidates  for   the   formation  of   a   superfluid  state in  two-dimensional  systems.  A  number   of   studies   reported observations   of   ultrafast nondiffusive   prop-agation  of  excitons  in  van  der  Waals  heterostructures,   which  was  considered by  their  authors  as possible  evidence  of collective  effects  in  excitonic  systems.   In   this   paper, after a brief analysis of exciton propagation regimes in  two-dimensional  semiconductors,  an alternative model  of  ultra-fast  exciton  transport  is  proposed,  based  on  the  formation   of  waveguide modes in van der Waals heterostructures and the radiation transfer by these modes.
Article for the special issue of JETP dedicated to the 130th anniversary of P. L. Kapitsa. 

It was shown how we can describe microscopically the Andreev current in a uniform way for a contact with direct coupling between N and S leads and with intermediate chain of atoms (multilayer system) inside the contact. Considering various types of connection of the normal lead to external thermal bath we reproduce various nonequilibrium distributions at the edge of the normal lead. It was shown what type of connection to the external reservoir corresponds to the classical result of Blonder,Klapwijk and Tinkham. Also we discuss difference in equilibrium and non equilibrium proximity effect, and it is clarified that the Andreev current arises due to the nonequilibrium effects which is much larger than the equilibrium one.
Contribution for the JETP special issue in honor of P. L. Kapitza’s 130th anniversary

The influence of spin-orbit interaction (SOI) on the distribution of spin and charge currents induced in a nonmagnetic conductor by an incident electromagnetic wave is investigated. The effect of SOI on conduction electron spin resonance (CESR) in metals is described. It is established that SOI can significantly alter the CESR line shape. It is shown that this circumstance can be used to determine the SOI magnitude in metal through precision measurements of CESR line asymmetry. The existence of CESR enhancement effect in metals with strong SOI is predicted. It is shown that SOI can lead to enhancement of selective spin transparency and that in a nonmagnetic metal, SOI-induced inversion of electromagnetic wave energy flow can occur – an effect consisting in the emergence of electromagnetic field energy flow directed towards the metal surface in the metal bulk.
Article for a special issue of JETP dedicated to the 130th anniversary of P. L. Kapitsa

Superconductivity and inhomogeneous states in metallic hydrogen and several electronic systems with attraction, described by inhomogeneous (spatially separated) Fermi–Bose mixture with superconducting clusters or order parameter droplets in a matrix of unpaired normal states, have been considered. The spatially separated Fermi–Bose mixture is realized in bismuth oxide superconductors BaKBiO₃. Order parameter droplets can appear in thin films of "dirty" (with high impurity content) metal, described by a two-dimensional Hubbard model of low electron density with strong attraction and strong diagonal disorder. In metallic hydrogen and metal hydrides, droplets and large percolation clusters can form in shock wave experiments near the first-order phase transition boundary between liquid (non-crystalline) metallic and dielectric phases. For homogeneous superconductivity in metallic hydrogen and metal hydrides, within the framework of generalized Eliashberg equations, new results were obtained demonstrating negative sign of derivative dTc / dP < 0, for the pressure range from 60 to 100 hPa in triple hydride LaBH₈. From the perspective of unusual physical properties, both in normal and possibly superfluid ("supersolid") states, important analogies between metallic hydrogen and quantum crystals have been highlighted.

Article for the special issue of JETP dedicated to the 130th anniversary of P. L. Kapitsa

We present theory of two-dimensional turbulence excited by an external force in thin fluid films on scales larger than the film thickness. The principal feature of two-dimensional turbulence is the tendency of producing motions of larger and larger scales thanks to the nonlinear interaction. The tendency leads to formation of the so-called inverse cascade and, at some conditions, of big coherent vortices. We discuss the mean velocity profile of the coherent vortices and the flow fluctuations on the background of the mean velocity for different regimes. We demonstrate that the regime of strongly interacting fluctuations leads to an anisotropic scaling inside the coherent vortices.

Possible manifestations of magnetic fields in the near-lunar plasma are considered. It is noted that due to the action of magnetic fields in the Earth's magnetotail, the transport of charged dust particles over large distances above the lunar surface is possible. Accordingly, dusty plasma above the sunlit lunar surface can exist for the entire range of lunar latitudes. Due to significant localization of magnetic anomaly regions, their influence on the transport of charged dust particles over the Moon is insignificant. Nevertheless, it is shown that in magnetic anomaly zones, dusty plasma is "suppressed" compared to the situation outside these zones dusty plasma. Important objects of study are mini-magnetospheres associated with lunar magnetic anomaly zones and responsible for a number of optical and satellite observations, such as "lunar swirls," lower-hybrid turbulence, etc.

Article for the special issue of JETP dedicated to the 130th anniversary of P. L. Kapitsa