Magnonic Analogue of Black/White Hole Horizon in Superfluid $^3$He-B

TL;DR

This paper presents a theoretical and experimental study of a magnonic analogue of black/white hole horizons in superfluid helium-3, demonstrating white hole formation, wave amplification, and potential for observing Hawking radiation at ultra-low temperatures.

Contribution

It introduces a novel experimental setup using spin supercurrents in superfluid helium-3 to simulate black/white hole horizons and provides evidence of white hole formation and wave amplification.

Findings

Evidence of white hole formation for spin precession waves

Observation of wave amplification effects

Estimated Hawking radiation temperature much lower than background

Abstract

We report on theoretical model and experimental results of the experiment made in a limit of absolute zero temperature ($\sim$ 600\,$\mu$K) studying the spin wave analogue of black/white hole horizon using spin (magnonic) superfluidity in superfluid $^3$He-B. As an experimental tool simulating the properties of the black/white horizon we used the spin-precession waves propagating on the background of the spin super-currents between two Bose-Einstein condensates of magnons in form of homogeneously precessing domains. We provide experimental evidence of the white hole formation for spin precession waves in this system, together with observation of an amplification effect. Moreover, the estimated temperature of the spontaneous Hawking radiation in this system is about four orders of magnitude lower than the system's background temperature what makes it a promising tool to study the effect of spontaneous Hawking radiation.