The role of geometry in the superfluid flow of nonlocal photon fluids

TL;DR

This paper demonstrates that by shaping the geometry of a nonlocal photon fluid, superfluid-like behavior such as vortex nucleation can be achieved despite inherent nonlocal interactions, opening new avenues for studying superfluid phenomena.

Contribution

The study shows that geometric tailoring of a thermal nonlocal photon fluid can induce superfluid characteristics, notably vortex formation, which was previously unexpected in such systems.

Findings

Elliptical laser profiles reduce nonlocal interaction length by two orders of magnitude.

Vortex nucleation occurs in photon flows with tailored geometry, indicating superfluid behavior.

Results are applicable to other nonlocal quantum fluids like dipolar BECs.

Abstract

Recent work has unveiled a new class of optical systems that can exhibit the characteristic features of superfluidity. One such system relies on the repulsive photon-photon interaction that is mediated by a thermal optical nonlinearity and is therefore inherently nonlocal due to thermal diffusion. Here we investigate how such a nonlocal interaction, which at a first inspection would not be expected to lead to superfluid behavior, may be tailored by acting upon the geometry of the photon fluid itself. Our models and measurements show that restricting the laser profile and hence the photon fluid to a strongly elliptical geometry modifies thermal diffusion along the major beam axis and reduces the effective nonlocal interaction length by two orders of magnitude. This in turn enables the system to display a characteristic trait of superfluid flow: the nucleation of quantized vortices in the flow past an extended physical obstacle. These results are general and apply to other nonlocal fluids, such as dipolar Bose-Einstein condensates, and show that "thermal" photon superfluids provide an exciting and novel experimental environment for probing the nature of superfluidity, with applications to the study of quantum turbulence and analogue gravity.