BCS to BEC Quantum Phase Transition in Spin Polarized Fermionic Gases

TL;DR

This paper explores a quantum phase transition in ultracold spin polarized fermionic gases, showing non-analytic behavior in physical properties as the system transitions between BCS and BEC regimes, driven by a Feshbach resonance.

Contribution

It demonstrates the non-analytic changes in compressibility, spin susceptibility, and superfluid density during the BCS-BEC transition in spin polarized fermionic gases.

Findings

Non-analyticity in compressibility and spin susceptibility at the transition.

Dramatic change in superfluid density across the critical point.

Ground state momentum distribution undergoes a massive rearrangement.

Abstract

We discuss the possibility of a quantum phase transition in ultracold spin polarized fermionic gases which exhibit a p-wave Feshbach resonace. We show that when fermionic atoms form a condensate that can be externally tuned between the BCS and BEC limits, the zero temperature compressibility and the spin susceptibility of the fermionic gas are non-analytic functions of the two-body bound state energy. This non-analyticity is due to a massive rearrangement of the momentum distribution in the ground state of the system. Furthermore, we show that the low temperature superfluid density is also non-analytic, and exibits a dramatic change in behavior when the critical value of the bound state energy is crossed.