Dynamical probing of superfluidity and shear rigidity in different phases of a dipolar Bose-Einstein condensate

TL;DR

This paper proposes a method using polarization changes to probe superfluidity and rigidity in dipolar Bose-Einstein condensates, revealing oscillation behaviors and phase transitions that distinguish different quantum phases.

Contribution

It introduces a novel experimental technique based on scissors mode oscillations to characterize superfluid and solid-like properties of dipolar BEC phases.

Findings

Superfluid state exhibits undamped scissors mode oscillation.

Droplet and supersolid states show damped scissors mode oscillations.

Damping rate correlates with phase rigidity and phase transition.

Abstract

We show that a sudden change in the polarization direction of the magnetic dipole moments of the atoms in a dipolar Bose-Einstein condensate (BEC) can serve as a useful probe to sense its superfluid and solid-like properties. We find that for small angular deviation of the polarization direction, actuated for instance by modifying an external magnetic field, the superfluid state undergoes an undamped scissors mode oscillation, a characteristic signature of superfluidity. In contrast, both the droplet and supersolid states exhibit a scissors-mode oscillation, which is effectively damped due to multiple closely spaced frequency components. Notably, we find that this damping rate provides a direct quantitative measure for the rigidity of different phases of a dipolar BEC. Furthermore, there exists a maximum angular deviation of the polarization direction, beyond which the droplet and the supersolid states undergo a permanent deformation i.e., we find an analog of the usual elastic to plastic phase transition of solids. We characterize this transition numerically using the fidelity of the condensate wavefunction with the ground state as well as the droplet width and periodicity of the supersolid density of the condensate which are experimentally accessible. Thus, the technique introduced here can be an important experimental benchmark to identify and characterize the superfluid and solid properties of different phases of dipolar BECs.