arXiv subjects

D. Hernández-Rajkov

Publications and source records attributed to D. Hernández-Rajkov.

3 recordsLinked to original sources

arXiv2025

Tuning the Critical Current in Toroidal Superfluids via Controllable Impurities

We combine numerical and experimental approaches to study how impurities affect the maximum superflow in an annular Bose-Einstein condensate. By tuning the impurity density, we achieve precise control over the stability of persistent currents which increases with the impurity number. In the unstable regime, the complex vortex motion within the impurity landscape, characterized by pinning and unpinning events, governs the timescale of the current decay and its final value. Our work establishes atomic superfluids as a pristine platform for exploring universal mechanisms of superflow stabilization and decay, paving the way for atomtronic quantum technologies.

cond-mat.quant-gas↗

arXiv2021

Faraday Waves in strongly interacting superfluids

We report on the observation of Faraday waves in a cigar-shaped Fermi superfluid of $^6$Li parametrically excited by modulating the radial trap frequency. We characterize the phenomenon as a function of the interaction parameter by means of a Feshbach resonance. Starting from the BEC side of the resonance we observe a drop on the visibility of the Faraday pattern as we approach to unitarity, possibly due to the increased incompressibility of the system. We probe the superfluid excitation spectrum by extracting an effective 1D speed of sound for different values of the interaction parameter, in good agreement with numerical simulations. Finally, we perform a stability analysis in the parameter space using a simplified model and we show the emergence of the Faraday waves as unstable solutions to a Mathieu-like equation.

cond-mat.quant-gas↗

arXiv2020

Experimental setup for the production of ultracold strongly correlated fermionic superfluids of $^{6}$Li

We present our experimental setup to produce ultracold strongly correlated fermionic superfluids made of a two-component spin-mixture of $^6$Li atoms. Employing standard cooling techniques, we achieve quantum degeneracy in a single-beam optical dipole trap. Our setup is capable of generating spin-balanced samples at temperatures as low as $T/T_F = 0.1$ containing up to $5 \times 10^4$ atomic pairs. We can access different superfluid regimes by tuning the interparticle interactions close to a broad magnetic Feshbach resonance. In particular, we are able to explore the crossover from the molecular Bose-Einstein condensate (BEC) to the Bardeen-Cooper-Schrieffer (BCS) superfluid regimes.

cond-mat.quant-gas↗