arXiv subjects

Buğra Tüzemen

Publications and source records attributed to Buğra Tüzemen.

7 recordsLinked to original sources

arXiv2026

Impurity-controlled vortex mobility and pair-breaking in fermionic superfluid rings

Using time-dependent density functional theory, we study how density and size of impurities govern dissipation of persistent currents of fermionic superfluid rings in the BCS regime. The critical winding number for vortex emission increases with impurity density, but this enhancement is impurity size-dependent and capped by the pair-breaking threshold. Below this vortex-emission threshold, the winding number remains constant while flow energy dissipates through impurity-enhanced pair-breaking. Above the threshold, vortex-impurity interactions produce distinct mobility regimes-deflected trajectories, individual pinning, collective pinning, and inter-site hopping, controlled by the impurity size and density, which determine the dominant dissipation channel. These findings provide design principles for ultracold-atom experiments and insights into vortex-pinning dynamics in neutron-star crusts and superconductors.

cond-mat.quant-gas↗

arXiv2025

Hierarchy of pairing in imbalanced three-component one-dimensional Fermi gas

We study a one-dimensional, three-component Fermi gas with population imbalance using the Bogoliubov-de Gennes mean-field approach. We specifically consider pairing in two channels while deliberately excluding the third by setting its interaction strength to zero. By systematically varying the interaction strength and population imbalance, we identify a rich set of spatially modulated superfluid states, including structures akin to the Larkin-Ovchinnikov phase and phase-separated domains. A clear hierarchy emerges in the pairing behavior, shaped by the competition between the local density of states and the Fermi momentum mismatch. A fidelity-based analysis of the density further distinguishes smooth crossovers from sharp spatial reorganizations. Our results shed light on how pairing symmetry and population imbalance determine the structure of spatially inhomogeneous superfluid phases in multicomponent systems with reduced dimensionality.

cond-mat.quant-gas↗

arXiv2023

Propagation properties and stability of dark solitons in weakly interacting Bose-Bose droplets

We investigate dark solitons in two-component Bose systems with competing interactions in one dimension. Such a system hosts a liquid phase stabilized by the beyond-mean field corrections. Using the generalized Gross-Pitaevskii equation, we reveal the presence of two families of solitonic solutions. The solitons in both of them can be engineered to be arbitrarily wide. One family of solutions, however, has got an anomalous dispersion relation and our analyses show one of its branches is unstable. We find the presence of a critical velocity demarcating the stable from unstable solutions. Nonetheless, grey anomalous solitons are able to exist inside quantum droplets and can be treated as solitonic excitations thereof.

cond-mat.quant-gas↗

arXiv2023

Disordered structures in ultracold spin-imbalanced Fermi gas

We investigate properties of spin-imbalanced ultracold Fermi gas in a large range of spin polarizations at low temperatures. We present results of microscopic calculations based on mean-field and density functional theory approaches, with no symmetry constraints. At low polarization values we predict the structure of the system as consisting of several spin-polarized droplets. As the polarization increases, the system self-organizes into a disordered structures similar to liquid crystals, and energetically they can compete with ordered structures such as grid-like domain walls. At higher polarizations the system starts to develop regularities that, in principle, can be called supersolid, where periodic density modulation and pairing correlations coexist. The robustness of the results has been checked with respect to temperature effects, dimensionality, and the presence of a trapping potential. Dynamical stability has also been investigated.

cond-mat.quant-gas↗

arXiv2021

Dynamics of spin-polarized impurity in ultracold Fermi gas

We show that the motion of spin-polarized impurity (ferron) in ultracold atomic gas is characterized by a certain critical velocity which can be traced back to the amount of spin imbalance inside the impurity. We have calculated the effective mass of ferron in two dimensions. We show that the effective mass scales with the surface of the ferron. We discuss the impact of these findings; in particular, we demonstrate that ferrons become unstable in the vicinity of a vortex.

cond-mat.quant-gas↗

arXiv2020

Properties of spin-polarized impurities -- ferrons, in the unitary Fermi gas

A new excitation mode has been predicted to exist in the unitary Fermi gas. It has a form of a spin-polarized impurity, which was dubbed as ferron. It is characterized by a closed nodal surface of the pairing field surrounding a partially spin-polarized superfluid region, where the phase differs by $π$. In this paper, we discuss the effect of temperature on the generation of the ferron and the adiabaticity of the spin-polarizing potential together with ferron's ground state properties.

cond-mat.quant-gas↗

arXiv2019

Spin-polarized droplets in the unitary Fermi gas

We demonstrate the existence of a new type of spatially localized excitations in the unitary Fermi gas: spin polarized droplets with a peculiar internal structure involving the abrupt change of the pairing phase at the surface of the droplet. It resembles the structure of the Josephson-$π$ junction occurring when a slice of a ferromagnet is sandwiched between two superconductors. The stability of the impurity is enhanced by the mutual interplay between the polarization effects and the pairing field, resulting in an exceptionally long-lived state. The prospects for its realization in experiment are discussed.

cond-mat.quant-gas↗