arXiv subjects

Aashish Kafle

Publications and source records attributed to Aashish Kafle.

3 recordsLinked to original sources

arXiv2025

Low Energy Excitations of a 1D Fermi Gas with Attractive Interactions

The low-energy excitations of a two-component repulsive Fermi gas confined to one dimension are linear dispersing spin- and charge-density waves whose respective propagation velocities depend on the strength and sign of their interaction. Quasi-1D fermions with attractive interaction realize the Luther-Emery liquid, which exhibits a rich array of phenomena, many of which are qualitatively different from those exhibited by their repulsive counterpart. We use a Feshbach resonance to access attractive interactions with $^6$Li atoms. We measured the spin and charge dynamic structure factors using Bragg spectroscopy and find that, contrary to repulsive interactions, the spin wave propagates faster than the charge density wave, thus producing an inversion of the classic spin-charge separation. We also find that a small spin polarization strongly suppresses the spin gap in the measured Bragg spectra. Evidence for pairing are a reduction in spin correlations with increasing attraction and RF spectra consistent with an atom/molecule mixture.

cond-mat.quant-gas↗

arXiv2023

Thermal disruption of a Luttinger liquid

The Tomonaga-Luttinger liquid (TLL) theory describes the low-energy excitations of strongly correlated one-dimensional (1D) fermions. In the past years, a number of studies have provided a detailed understanding of this universality class. More recently, theoretical investigations that go beyond the standard low-temperature, linear-response, TLL regime have been developed. While these provide a basis for understanding the dynamics of the spin-incoherent Luttinger liquid, there are few experimental investigations in this regime. Here we report the observation of a thermally-induced, spin-incoherent Luttinger liquid in a $^6$Li atomic Fermi gas confined to 1D. We use Bragg spectroscopy to measure the suppression of spin-charge separation and the decay of correlations as the temperature is increased. Our results probe the crossover between the coherent and incoherent regimes of the Luttinger liquid, and elucidate the roles of the charge and the spin degrees of freedom in this regime.

cond-mat.quant-gas↗

arXiv2022

Spin-charge separation in a 1D Fermi gas with tunable interactions

Ultracold atoms confined to periodic potentials have proven to be a powerful tool for quantum simulation of complex many-body systems. We confine fermions to one-dimension to realize the Tomonaga-Luttinger liquid model describing the highly collective nature of their low-energy excitations. We use Bragg spectroscopy to directly excite either the spin or charge wave for various strength of repulsive interaction. We observe that the velocity of the spin and charge excitations shift in opposite directions with increasing interaction, a hallmark of spin-charge separation. The excitation spectra are in quantitative agreement with the Tomonaga-Luttinger liquid theory, and furthermore, we find that the spin excitations become dispersive at large interaction, signaling the onset of the nonlinear Luttinger liquid regime.

cond-mat.quant-gas↗