Unconventional pairing in one-dimensional systems of a few mass-imbalanced ultracold fermions

Abstract

We study the ground-state properties of a two-component fermionic mixture effectively confined in a one-dimensional harmonic trap. We consider scenarios when numbers of particles in components are the same but particles have different masses. We examine whether it is possible to detect signatures of an unconventional pairing between opposite-spin fermions in the presence of attractive interactions. For this purpose, we perform the exact diagonalization of the many-body Hamiltonian and study the two-particle reduced density matrix. In agreement with expectations, we confirm that the many-body ground state is dominated by conventional pairs with a negligible total momentum for a small mass imbalance. Furthermore, we show that for sufficiently large mass ratios the domination of fundamentally different pairs is established and the Fulde-Ferrel-Larkin-Ovchinnikov phase is supported. Finally, we argue that the two mechanisms can coexist in the regime of moderate mass ratios. In view of the current experimental progress in obtaining ultra-cold fermionic systems in a few-body regime, our predictions can be validated in the state-of-the-art experiments.arXiv:1911.04188v1 [cond-mat.quant-gas]

Unconventional pairing in few-fermion systems tuned by external confinement

“…For the attractive inter-component interactions (g < 0), fermions of opposite species form strongly correlated pairs. It has been shown that these pairs may display many different features of the Cooper pairs known from the theory of superconductivity [44][45][46][47][48]. Identifying the type of pairing that arises (i.e.…”

Pairing patterns in one-dimensional spin- and mass-imbalanced Fermi gases

“…Recently, studies based on ED explored shot-noise correlations [82] and a related measure [83] to study the influence of mass imbalance on pair formation in harmonically trapped spin-balanced few-body systems have also been performed. In the present work, however, we address this quantity in the presence of spin imbalance for many-body systems and show that unambiguous features emerge which can potentially be identified in currently available experimental setups.…”

Simulating Artificial 1D Physics with Ultra‐Cold Fermionic Atoms: Three Exemplary Themes

“…For this reason, the unconventional FFLO pairing in ultra‐cold 1D systems has recently been deeply investigated theoretically from various perspectives, for both confined [ 54–57 ] and lattice systems. [ 58–62 ] Quasi‐1D quantum simulators created with ultra‐cold neutral atoms constitute a highly controllable environment, where the Fermi surface mismatch can be precisely tuned by changing the spin composition of the initial population, rather than with external magnetic fields.…”