P-wave Pairing in Two-Component Fermi Systems with Unequal Population near Feshbach Resonance

TL;DR

This paper investigates p-wave superfluid pairing in a two-component Fermi system with population imbalance near a Feshbach resonance, revealing complex ground states, phase transitions, and a detailed phase diagram.

Contribution

It provides a comprehensive analysis of p-wave pairing states, including mixed states and phase stability, in imbalanced Fermi systems near resonance, with geometric and phase diagram insights.

Findings

Multiple superfluid states including mixed states are identified.

A phase diagram of polarization versus p-wave coupling is constructed.

Quantum phase transitions between superfluid states are observed.

Abstract

We explore p-wave pairing in a single-channel two-component Fermi system with unequal population near Feshbach resonance. Our analytical and numerical study reveal a rich superfluid (SF) ground state structure as a function of imbalance. In addition to the state $\Delta_{\pm 1} \propto Y_{1\pm 1}$, a multitude of ``mixed'' SF states formed of linear combinations of $Y_{1m}$'s give global energy minimum under a phase stability condition; these states exhibit variation in energy with the relative phase between the constituent gap amplitudes. States with local energy minimum are also obtained. We provide a geometric representation of the states. A $T$=0 polarization vs. p-wave coupling phase diagram is constructed across the BEC-BCS regimes. With increased polarization, the global minimum SF state may undergo a quantum phase transition to the local minimum SF state.