arXiv subjects

Parth Sabharwal

Publications and source records attributed to Parth Sabharwal.

5 recordsLinked to original sources

arXiv2024

Thermal Phase Fluctuations in Narrow Superfluid Rings

Using matter-wave interference, we have investigated thermal phase fluctuations in narrow coplanar, concentric rings of ultracold fermionic superfluids. We found that the correlation length decreases with number density, consistent with theoretical expectations. We also observed that increasing the coupling between the rings leads to greater overall coherence in the system. The phase fluctuations increased with a change from periodic to closed boundary conditions as we applied a potential barrier at one point in a ring. These results are relevant for the implementation of proposals to utilize ultracold quantum gases in large and elongated circuit-like geometries, especially those that require deterministic preparation and control of quantized circulation states.

cond-mat.quant-gas↗

arXiv2023

Quench-induced spontaneous currents in rings of ultracold fermionic atoms

We have observed the spontaneous appearance of currents in a ring of ultracold fermionic atoms (6Li) with attractive interactions, following a quench to a BCS-like pair superfluid. We have measured the winding number probability distribution for a range of quench rates, with a quench protocol using simultaneous forced evaporation and interaction ramps to achieve faster effective quench rates with less atom loss than a purely evaporative quench. We find that for the fastest quenches the mean square winding number of the current follows a scaling law in the quench rate with exponent {\sigma} = 0.24(2), which is somewhat lower than that predicted by the Kibble-Zurek mechanism (KZM) for the three-dimensional XY model (1/3), and unexpectedly closer to the value obtained from mean-field theory (1/4). For slower quenches non-universal effects become significant, and we observe a lower rate of spontaneous current formation that does not follow a simple scaling law.

cond-mat.quant-gas↗

arXiv2022

Mitigating Heating of Degenerate Fermions in a Ring-Dimple Atomic Trap

We report on the impact of the extended geometry of a ring-dimple trap on particle loss heating of a degenerate Fermi gas. When the Fermi level is slightly greater than the depth of the dimple and a non-degenerate "halo" is present, the overall heating rate is reduced relative to the case of a bare ring. We find that the experimentally measured heating rates for the overfilled dimple are in good agreement with a model of the hole-induced heating caused by background gas collisions. This suppression of the heating rate can be helpful for experimental studies of fermionic superfluids in the weak pairing limit, where achieving and maintaining low temperatures over long time scales is essential.

cond-mat.quant-gas↗

arXiv2021

Persistent currents in rings of ultracold fermionic atoms

We have produced persistent currents of ultracold fermionic atoms trapped in a ring, with lifetimes greater than 10 seconds in the strongly-interacting regime. These currents remain stable well into the BCS regime at sufficiently low temperature. We drive a circulating BCS superfluid into the normal phase and back by changing the interaction strength and find that the probability for quantized superflow to reappear is remarkably insensitive to the time spent in the normal phase and the minimum interaction strength. After ruling out spontaneous current formation for our experimental conditions, we argue that the reappearance of superflow is due to weak damping of normal currents in this limit. These results establish that ultracold fermionic atoms with tunable interactions can be used to create matter-wave circuits similar to those previously created with weakly-interacting bosonic atoms.

cond-mat.quant-gas↗

arXiv2020

Monolithic bowtie cavity traps for ultra-cold gases

We report on trapping and cooling Li-6 atoms in a monolithic ring bowtie cavity. To make the cavity insensitive to magnetic fields used to tune atomic interactions, we constructed it entirely from fused silica and Zerodur. The components were assembled using hydroxide bonding, which we show can be compatible with ultra-high vacuum. Backscattering in high-finesse ring cavities readily causes trap intensity fluctuations and heating, but with phase-controlled bi-directional pumping the trap lifetime can be made long enough for quantum gas experiments in both the crossed-beam trap (unidirectional pump) and 2D lattice trap (bidirectional pump) configurations.

cond-mat.quant-gas↗