Spontaneous inhomogeneous phases in ultracold dipolar Fermi gases

TL;DR

This paper investigates how strong dipolar interactions cause ultracold fermionic gases to form inhomogeneous phases like stripes and phase separation in 2D and 3D, with theoretical proofs and implications for experiments.

Contribution

It provides a theoretical analysis of the emergence of stripe and phase separation in ultracold dipolar Fermi gases, highlighting the role of dimensionality and critical dipole moments.

Findings

Stripe phase always favored in 2D for dipole moments above critical value.

In 3D, phase separation is the dominant instability.

Theoretical proof of stripe phase stability in 2D.

Abstract

We study the collapse of ultracold fermionic gases into inhomogeneous states due to strong dipolar interaction in both 2D and 3D. Depending on the dimensionality, we find that two different types of inhomogeneous states are stabilized once the dipole moment reaches a critical value $d>d_c$: the {\it stripe phase} and {\it phase separation} between high and low densities. In 2D, we prove that the stripe phase is always favored for $d\gtrsim d_c$, regardless of the microscopic details of the system. In 3D, the one-loop perturbative calculation suggests that the same type of instability leads to phase separation. Experimental detection and finite-temperature effects are discussed.