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Iogann Tolbatov

Publications and source records attributed to Iogann Tolbatov.

12 recordsLinked to original sources
arXiv2026

Altermagnetism across the BCS-BEC crossover

We study a two-dimensional paired Fermi system in which altermagnetism produces a spin splitting that depends on momentum. The interaction strength is described through the two-body binding energy, so that the chemical potential and pairing gap evolve self-consistently from the weak-coupling Bardeen-Cooper-Schrieffer (BCS) regime to the strong-coupling Bose-Einstein-condensate (BEC) regime at fixed density. The stability of the uniform paired state is examined by giving the pairs a small center-of-mass momentum and following the resulting change in free energy. We show that at zero temperature, the phase stiffness follows a universal quadratic suppression, $J/J_0 = 1 - (α/α_0)^2$, across the entire fully gapped crossover regime. Deviations from this relation emerge only on the BCS side upon the opening of gapless Bogoliubov pockets, which rapidly reduce the stiffness and can trigger an instability toward finite-momentum pairing. In the BEC regime, this universal quadratic correction corresponds to the altered effective mass of the tightly bound composite bosons. The model therefore provides a simple setting in which to compare altermagnetic pair breaking on the BCS and BEC sides of the crossover.

cond-mat.supr-con↗
arXiv2026

Electrostatic lens of a charged vortex

We study the local electrostatic response of a charged superfluid in the presence of a cylindrically symmetric vortex, allowing both the particle density and the thermodynamic compressibility to vary with the radial coordinate. Starting from the electrostatic charge response obtained from the phase-only Popov action, we introduce a local-density extension and derive the regular near-axis expansion of the scalar potential. The constant, quadratic, and quartic coefficients are obtained explicitly in terms of the local screening response and of the leading nonuniform contribution to the vortex density profile. For a three-dimensional unitary Fermi equation of state, the density dependence of the compressibility generates a definite thermodynamic contribution to the quartic coefficient. The resulting decomposition separates this equation-of-state contribution from the ordinary constant-screening and charge-source terms that occur at the same order. This provides a compact analytical connection between vortex-core thermodynamics and the local electrostatic profile of a charged superfluid.

cond-mat.supr-con↗
arXiv2026

Superdiffusive two-dimensional superconductors

We formulate a non-local, field-theoretic description of phase fluctuations and topological transitions in two-dimensional (2D) superconductors by generalizing the local only-phase Popov action to a framework utilizing non-local fractional operators. By replacing the standard spatial Laplacian with the Riesz fractional Laplacian $-(-\nabla^2)^{α/2}$ (where $1<α<2$), we prove that the vortex-antivortex interaction transitions from logarithmic confinement to a stronger power-law confinement of the form $V(r)\propto r^{2-α}$. Through a generalized Kosterlitz-Thouless energetic-entropic analysis, we demonstrate that this non-local confinement strictly suppresses thermal vortex proliferation. Because the non-local operator safely places the system outside the strict domain of validity of the Mermin-Wagner restriction, this power-law confinement natively stabilizes true long-range order at finite temperatures. Finally, by constructing a gauge-invariant fractional action, we formulate a fractional London equation. This approach yields a real-space power-law kernel that maps directly onto the anomalous Pippard limit of superconductors with long coherence lengths, providing a unified phenomenologically motivated framework for non-local electrodynamics.

cond-mat.supr-con↗
arXiv2015

A study of stability of the "plasma - beam" system for the Lorentz plasma

The stability of the system comprising the cold immobile Lorentz plasma of density $N_e$ and the directed nonrelativistic (velocity $\vec{V}$) electronic beam of a small density $N'_e << N_e$ is investigated. The instability increment of the system is found via analysis of the electric permittivity $ε(ω)$ in the limiting case of $ω$ being much greater than the effective frequency of collisions. A conclusion is made that the system in question is stable with respect to oscillations with relatively small values of $\vec{k} \vec{V}$.

physics.plasm-ph↗
arXiv2009

Superconducting nanodrop model

Superconducting nanodrop model is constructed on the basis of the assumption of equality of the free energy functional gradient term to zero due to the order parameter value constancy in the superconducting nanodrop volume. In the investigation, we have defined the superconducting nanodrop thermodynamical characteristics: partition function, the magnitudes of the jumps in entropy and specific heat at the second order phase transition, total energy, energy fluctuation, specific heat, free energy, and entropy.

cond-mat.supr-con↗
arXiv2009

To the identification of universal criterion of the charged particles system stability

We consider the problem important for the condensed matter physics, superconductivity physics, and electrodynamics of continuous media - the problem of the matter dielectric permittivity possible values spectrum definition. Two ways of the dielectric permittivity values spectrum identification are analyzed. The proposed technique allows the author to complete the universal criterion of stability identified by D. A. Kirzhnits for a system of charged particles by the criterion of stability for a superconducting system of charged particles.

physics.gen-ph↗
arXiv2009

To the low-temperature technologies methodology: the clean superconductor free energy fluctuations calculation in the micro- and macrostructures descriptions of superconductor

The Ginzburg - Landau theory is used for the superconducting structures free energy fluctuations study. On its basis, we have defined the value of the heat capacity jump in the macroscopic zero-dimensional sample and in the zero-dimensional microstructures ensemble of the total volume equal to the macroscopic sample volume. The inference is made that in the Ginzburg - Landau methodology frameworks, it is essential to take into account the superconducting clean sample effective dimensionality only on the last stage of its thermodynamical characteristics calculation.

physics.gen-ph↗
arXiv2009

Criterion of stability of the superconducting state

In this paper, we propose to draw attention to the stability criterion of the superconductor current state. We use for this purpose the rough systems mathematical apparatus allowing us to relate the desired criterion with the dielectric permittivity of the matter and to identify the type of all possible phonons trajectories in its superconducting state. The state of superconductivity in the matter can be explained only by the phonons behavior peculiarity. And on the basis of the above-mentioned assumption, the corresponding mathematical model is constructed.

physics.gen-ph↗
arXiv2009

Investigation of electrons interaction in a superconductor

Investigating the interaction of electrons in a superconductor by means of a method of solitary waves of Korteweg - de Vries, we refute the claim of absence of "Cooper pairs" in a superconductor. We also indicate that the nondissipative transfer of energy in the superconductor is possible only with the help of a pair of electrons.

physics.gen-ph↗
arXiv2009

To the methodology of low temperature technologies: mathematical analysis of Langevin forces in superconductor

Langevin forces are investigated in the framework of the phenomenological Ginzburg-Landau (GL) theory. These stochastic forces introducted in the time-dependent Ginzburg-Landau (TDGL) equation describing the superconductor transport properties above the critical temperature model the fluctuations action. We assume that there exists a profound connection between the fluctuation Cooper pair energy spectrum and the Langevin forces possible values spectrum. In investigation carried out on the basis of that hypothesis we obtain the analytical expression for Langevin forces defining them by means of order parameter, i.e., by means of the fluctuation Cooper pair wave function. Langevin forces properties are analyzed. The conlusion about their complex nature is done. Asymptotic analysis of Langevin forces is performed.

cond-mat.supr-con↗
arXiv2009

Influence of fluctuations on the superfluid density in low-temperature technologies

In this article the Ginzburg-Landau theory ideas are considered in their application to the description of fluctuations influence on the superfluid density in superconductor. The conclusion about the availability of two incompatible mathematical definitions of the superfluid density is made. That is why, it is suggested not to consider the fluctuating part of order parameter, while calculating the superconductor thermodynamical characteristics in the Mean Field Approximation.

cond-mat.supr-con↗