arXiv subjects

M. Bulakhov

Publications and source records attributed to M. Bulakhov.

4 recordsLinked to original sources

arXiv2026

Multipolar exchange in a many-body homonuclear mixture of atoms in different internal states

We develop a general method for constructing the many-body Hamiltonian of pairwise interactions describing homonuclear mixtures of atoms occupying states with different total angular momenta or other quantum numbers. The advantage of the irreducible spherical tensor operator formalism is demonstrated: these operators give the Hamiltonian an explicit physical structure, account for all scattering channels, and include multipolar exchange interactions. The latter correspond to the exchange of both angular-momentum projections and the total angular momentum. Particular realizations of the general Hamiltonian, widely used in the physics of ultracold gases, are also analyzed. The resulting Hamiltonian provides a universal framework for investigating a broad range of quantum many-body phenomena in bosonic and fermionic atomic gases.

cond-mat.quant-gas↗

arXiv2025

Self-consistent Hartree-Fock-Bogoliubov approach for bosons: self-eliminating divergence and pure pair condensate

We investigate the thermodynamic properties of an interacting Bose gas with a condensate within the energy-functional formulation of the Hartree-Fock-Bogoliubov (HFB) approach. For a contact interaction, we derive a self-consistent solution to the HFB equations that intrinsically eliminates divergence. This solution characterizes the equilibrium state featuring a condensate of correlated pairs of particles. We analyze the temperature dependence of key thermodynamic quantities such as condensate density, chemical potential, entropy, pressure, specific heat capacity at constant volume, and isothermal compressibility and compare them with predictions from the Popov approximation (PA). We predict that the transition temperature shifts to higher values due interactions, with the HFB approach yielding a larger shift than the PA. Analysis of the compressibility indicates that a pure pair condensate is unstable, and the stable equilibrium corresponds to only a mixture of single-particle and pair condensates.

cond-mat.quant-gas↗

arXiv2024

General collisionless kinetic approach to studying excitations in arbitrary-spin quantum atomic gases

We develop a general kinetic approach to studying high-frequency collective excitations in arbitrary-spin quantum gases. To this end, we formulate a many-body Hamiltonian that includes the multipolar exchange interaction as well as the coupling of a multipolar moment with an external field. By linearizing the respective collisionless kinetic equation, we find a general dispersion equation that allows us to examine the high-frequency collective modes for arbitrary-spin atoms obeying one or another quantum statistics. We analyze some of its particular solutions describing spin waves and zero sound for Bose and Fermi gases.

cond-mat.quant-gas↗

arXiv2023

Zero sound in a quantum gas of spin-3/2 atoms with multipole exchange interaction

In the context of quantum gases, we obtain a many-body Hamiltonian for spin-3/2 atoms with general multipole (spin, quadrupole, and octupole) exchange interaction by employing the apparatus of irreducible spherical tensor operators. This Hamiltonian implies the finite-range interaction, whereas, for zero-range (contact) potentials parameterized by the $s$-wave scattering length, the multipole exchange interaction becomes irrelevant. Following the reduced description method for quantum systems, we derive the quantum kinetic equation for spin-3/2 atoms in a magnetic field and apply it to examine the high-frequency oscillations known as zero sound.

cond-mat.quant-gas↗