Browsing by Author "Chang, Ya-Ting"
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Item Collisional loss of one-dimensional fermions near a p-wave Feshbach resonance(2021-05-13) Chang, Ya-Ting; Hulet, Randall G.The prospect of using Majorana fermions for application to fault-tolerant quantum computation has recently received much attention. Majorana fermions can be created in $p_x + ip_y$ topological superfluids or at the ends of a 1D $p$-wave superfluid. Exploring $p$-wave pairing in ultracold atomic gases has been difficult due to severe atom loss from three-body recombination near a $p$-wave Feshbach resonance. Three-body loss is predicted to be suppressed, however, in quasi-one-dimensional (quasi-1D), due to the extended wavefunctions of the open-channel dominant Feshbach dimers. In this work, we have experimentally studied collisional loss of a quasi-1D spin-polarized Fermi gas near a $p$-wave Feshbach resonance using ultracold $^6$Li atoms confined to a 2D optical lattice. We measured the atom loss as a function of time and extracted the three-body recombination rate, $L_3$. We also analyzed the atom loss as a two-step cascade three-body recombination model, in which weakly bound dimers are formed prior to their loss arising from atom-dimer collisions. In this thesis, the comparison of the experimental results and the theoretical predictions are presented. The implications of these measurements for observing $p$-wave pairing in quasi-1D are discussed in this thesis.Item Spin-charge separation in a 1D Fermi gas with tunable interactions(AAAS, 2022) Senaratne, Ruwan; Cavazos-Cavazos, Danyel; Wang, Sheng; He, Feng; Chang, Ya-Ting; Kafle, Aashish; Pu, Han; Guan, Xi-Wen; Hulet, Randall G.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, which describes the highly collective nature of their low-energy excitations. We use Bragg spectroscopy to directly excite either the spin or charge waves for various strengths 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 exact solution of the Yang-Gaudin model and the Tomonaga-Luttinger liquid theory. Furthermore, we identify effects of nonlinear corrections to this theory that arise from band curvature and back-scattering.