Superradiant phononic emission from the analog spin ergoregion in a two-component Bose-Einstein condensate

TL;DR

This paper explores hydrodynamic instabilities and superradiant phonon emission in two-component Bose-Einstein condensates, using analog gravity to model ergoregion phenomena similar to rotating astrophysical objects.

Contribution

It demonstrates how two-component condensates can serve as analog models for ergoregion instabilities and superradiance in rotating space-times, revealing new dynamical behaviors.

Findings

Identification of localized vortex splitting instabilities

Discovery of extended unstable modes involving phonon superradiance

Confirmation of condensates as versatile analog models for gravitational phenomena

Abstract

We make use of an analog gravity perspective to obtain a physical understanding of hydrodynamic instabilities stemming from the presence of quantized vortices in two-component atomic condensates and of their relation to ergoregion instabilities of rotating massive objects in gravitation. In addition to the localized instabilities related to vortex splitting, configurations displaying dynamically unstable modes that extend well outside the vortex core are found. In this case, the superradiant scattering process involves phonon emission into the much wider ergoregion of spin modes, so the physics most closely resembles the one of rotating massive objects. Our results confirm the potential of two-component condensates as analog models of rotating space-times in different regimes of gravitational interest.