arXiv subjects

A. V. Turlapov

Publications and source records attributed to A. V. Turlapov.

6 recordsLinked to original sources

arXiv2026

Transformation of the Talbot effect in response to phase disorder

Bose-Einstein condensates initially arranged in a long chain freely expand and interfere. If the initial phases of the condensates are identical, the initial density distribution is restored periodically during the expansion, giving rise to the Talbot effect. Even a slight disorder in the initial phases leads to a transformation of the interference pattern. In response to the phase disorder, the spectrum of the spatial density distribution acquires peaks that are absent in the case of identical phases. We derive an analytical expression for the spectrum of the spatial density distribution for an arbitrary phase disorder. We show that the new peaks emerging due to the phase disorder originate from pairwise interferences of the condensates. The positions of these peaks coincide with the wave vectors of the density modulations (wavelets) generated by such pairwise interferences. The absence of these peaks, when the initial phases are identical, is explained by the mutual destruction of the overlapping wavelets during their summation.

cond-mat.quant-gas↗

arXiv2026

Interference of a chain of Bose condensates in the Pitaevskii-Gross approximation

A long chain of Bose condensates freely expands and interferes after being released from an optical lattice. The interference fringes are well resolved both in the case of equal phases of the condensates and in the case of fluctuating phases. In the second case the positions of the fringes also fluctuate. The spectrum of the spatial density distribution, however, is reproducible despite the fluctuations. Moreover two types of peaks are distinguishable in the spectrum. The first type arises due to the phase fluctuations, the second type is associated with the coherence between the condensates. In the framework of the Pitaevskii-Gross equation we calculate the interference of the condensates and compare the calculation with experiment [Phys. Rev. Lett. 122, 090403 (2019)]. The calculation reproduces the positions of the spectrum peaks, including the dependence on the interparticle interaction. The calculated heights of the peaks, however, in some cases differ with the experimental ones.

cond-mat.quant-gas↗

arXiv2023

Formation of droplets of the order parameter and superconductivity in inhomogeneous Fermi-Bose mixtures (Brief review)

The studies of a number of systems treated in terms of an inhomogeneous (spatially separated) Fermi-Bose mixture with superconducting clusters or droplets of the order parameter in a host medium with unpaired normal states are reviewed. A spatially separated Fermi-Bose mixture is relevant to superconducting BaKBiO3 bismuth oxides. Droplets of the order parameter can occur in thin films of a dirty metal, described in the framework of the strongly attractive two-dimensional Hubbard model at a low electron density with a clearly pronounced diagonal disorder. The Bose-Einstein condensate droplets are formed in mixtures and dipole gases with an imbalance in the densities of the Fermi and Bose components. The Bose-Einstein condensate clusters also arise at the center or at the periphery of a magnetic trap involving spin-polarized Fermi gases. Exciton and plasmon collapsing droplets can emerge in the presence of the exciton-exciton or plasmon-plasmon interaction. The plasmon contribution to the charge screening in MgB2 leads to the formation of spatially modulated inhomogeneous structures. In metallic hydrogen and metal hydrides, droplets can be formed in shock-wave experiments at the boundary of the first-order phase transition between the metallic and molecular phases. In a spatially separated Fermi-Bose mixture arising in an Aharonov-Bohm interference ring with a superconducting bridge in a topologically nontrivial state, additional Fano resonances may appear and collapse due to the presence of edge Majorana modes in the system.

cond-mat.mes-hall↗

arXiv2019

The quantum Talbot effect for a chain of partially correlated Bose-Einstein condensates

The matter-wave interference picture, which appears within the quantum Talbot effect, changes qualitatively in response to even a small randomness in the phases of the sources. The spatial spectrum acquires peaks which are absent in the case of equal phases. The mathematic model of the effect is presented. The manifestations of the phase randomness in experiments with atomic and molecular Bose condensates, is discussed. Thermometry based on observable consequences of phase randomness is proposed.

cond-mat.quant-gas↗

arXiv2019

Expansion of the strongly interacting superfluid Fermi gas: symmetries and self-similar regimes

We consider an expansion of the strongly interacting superfluid Fermi gas in a vacuum, assuming absence of the trapping potential, in the so-called unitary regime (see, for instance, \cite{pitaevskii2008superfluid}) when the chemical potential $μ\propto \hbar^2n^{2/3}/m$ where $n$ is the density of the Bose-Einstein condensate of Cooper pairs of fermionic atoms. In low temperatures, $T\to 0$, such expansion can be described in the framework of the Gross-Pitaevskii equation (GPE). Because of the chemical potential dependence on the density, $\sim n^{2/3}$, the GPE has additional symmetries, resulting in the existence of the virial theorem \cite% {vlasov1971averaged}, connecting the mean size of the gas cloud and its Hamiltonian. It leads asymptotically at $t\to\infty$ to the gas cloud expansion, linearly growing in time. We study such asymptotics, and reveal the perfect match between the quasi-classical self-similar solution and the asymptotic expansion of the non-interacting gas. This match is governed by the virial theorem, derived through utilizing the Talanov transformation \cite{talanov1970focusing}, which was first obtained for the stationary self-focusing of light in media with a cubic nonlinearity due to the Kerr effect. In the quasi-classical limit, the equations of motion coincide with 3D hydrodynamics for the perfect monoatomic gas with $γ=5/3$. Their self-similar solution describes, on the background of the gas expansion, the angular deformities of the gas shape in the framework of the Ermakov--Ray--Reid type system.

cond-mat.quant-gas↗

arXiv2017

Fermi-to-Bose crossover in a trapped quasi-2D gas of fermionic atoms

Physics of many-body systems where particles are restricted to move in two spatial dimensions is challenging and even controversial: On one hand, neither long-range order nor Bose condensation may appear in infinite uniform 2D systems at finite temperature, on the other hand this does not prohibit superfluidity or superconductivity. Moreover, 2D superconductors, such as cuprates, are among the systems with highest critical temperatures. Ultracold atoms are a platform for studying 2D physics. Uniquely to other physical systems, quantum statistics may be completely changed in an ultracold gas: an atomic Fermi gas may be smoothly crossed over into a gas of Bose molecules (or dimers) by tuning interatomic interactions. We review recent experiments where such crossover has been demonstrated as well as critical phenomena in the Fermi-to-Bose crossover. We also present simple theoretical models describing the gas at different points of the crossover and compare the data to these and more advanced models.

cond-mat.quant-gas↗