Exploring the order parameter symmetry of p-wave Fermi condensates

TL;DR

This paper investigates how the anisotropic expansion of p-wave Fermi superfluids during time-of-flight experiments reveals the symmetry of their order parameter, providing a method to probe superfluid pairing states.

Contribution

It demonstrates that p-wave superfluids exhibit anisotropic expansion patterns sensitive to interaction parameters and magnetic fields, unlike s-wave or Bose condensates, enabling symmetry characterization.

Findings

P-wave superfluids expand anisotropically even in isotropic traps.

Expansion anisotropy depends on interaction strength and magnetic field orientation.

Aspect ratio inversion occurs during expansion, indicating underlying anisotropic interactions.

Abstract

We discuss the time-of-flight expansion of dilute p-wave Fermi condensates on the BEC side of Feshbach resonances, as a way to extract information about the order parameter symmetry for superfluidity. We show that the cloud profile is in general sensitive to the interaction strength between fermions, the magnitude and direction of external magnetic fields, and to the angular momentum projection of the order parameter. In particular, due to the anisotropic nature of p-wave interactions we show that the time-of-flight expansion of a p-wave superfluid is anisotropic even if the superfluid is confined to a completely isotropic trap, unlike the case of Bose or s-wave Fermi condensates, which under the same circumstances expand isotropically. Furthermore, we demonstrate that expanding p-wave superfluids released from axially symmetric traps experience anisotropy inversions, where the aspect ratio between the axial and radial directions change during expansion, while the axial symmetry can also be lost reflecting the spatial anisotropy of the underlying interaction.