Equation of State and Phases of Polarized Unitary Fermi Gas

TL;DR

This paper uses ab initio Monte Carlo simulations to determine the phase diagram and equations of state of a polarized unitary Fermi gas at zero temperature, revealing critical polarization thresholds and phase boundaries.

Contribution

It provides the first ab initio calculations of phase transitions and equations of state for polarized unitary Fermi gases, including critical chemical potential ratios and trap phase boundaries.

Findings

Critical chemical potential ratio for superfluid transition is 0.11.

Critical ratio for normal phase transition is -0.59.

Superfluid core disappears beyond 0.65 polarization in traps.

Abstract

The equation of state of the partially polarized two component Fermi gas at zero temperature in the unitary limit is computed by {\it ab initio} auxiliary field Monte Carlo method. We obtain the critical ratio of the chemical potentials $\mu_\downarrow/\mu_\uparrow$ at the phase transitions. The value of $\mu_\downarrow/\mu_\uparrow$ at the transition between the fully paired superfluid and the partially polarized phase is 0.11 while the critical value for the phase transition between the partially polarized phase and the fully polarized normal fluid is -0.59. We also determine the radial boundaries of the phase transitions of the Fermi gas in the harmonic trap as function of the total polarization. We find that beyond the critical polarization 0.65, the fully paired superfluid core disappears in the trapped Fermi gas.