Trap-imbalanced fermion mixtures

TL;DR

This paper investigates the phase structure of trap-imbalanced fermion mixtures across interaction regimes, revealing how superfluid and normal phases spatially evolve from BCS to BEC limits.

Contribution

It provides a detailed analysis of how trap imbalance affects phase separation and superfluidity in fermion mixtures across the BCS-BEC crossover.

Findings

Unpolarized superfluid exists away from trap center in the BCS limit.

Central partially polarized normal phase transitions to superfluid with increasing interaction.

Entire mixture becomes superfluid in the BEC limit.

Abstract

We analyze the ground state phases of two-component ($\sigma \equiv \lbrace \uparrow, \downarrow \rbrace$) population- and mass-balanced ($N_\uparrow = N_\downarrow$ and $m_\uparrow = m_\downarrow$) but trap-imbalanced ($\omega_\uparrow \ne \omega_\downarrow$) fermion mixtures as a function of interaction strength from the weak attraction Bardeen-Cooper-Schrieffer (BCS) to the strong attraction Bose-Einstein condensation (BEC) limit. In the BCS limit, we find that the unpolarized superfluid (UPS) fermions exist away from the central core of the trapping potentials, and are surrounded by partially polarized normal (P$\sigma$PN) fermions. As the interactions increase towards unitarity, we find that the central P$\sigma$PN core first transitions to a UPS, and then expands towards the edges until the entire mixture becomes a UPS in the BEC limit.