Self-localization of magnon Bose-Einstein condensates in the ground state and on excited levels: from harmonic to box-like trapping potential

TL;DR

This paper demonstrates the self-localization of magnon Bose-Einstein condensates in different trap geometries, including harmonic and box-like potentials, and explores their coexistence at various energy levels.

Contribution

It provides the first experimental evidence of Bose condensation in a box-like trap and shows control over condensate states via rf pumping.

Findings

Transition from harmonic to box-like trap observed

Coexistence of condensates at different energy levels demonstrated

Trap profile can be manipulated experimentally

Abstract

Long-lived coherent spin precession of 3He-B at low temperatures around 0.2 Tc is a manifestation of Bose-Einstein condensation of spin-wave excitations or magnons in a magnetic trap which is formed by the order-parameter texture and can be manipulated experimentally. When the number of magnons increases, the orbital texture reorients under the influence of the spin-orbit interaction and the profile of the trap gradually changes from harmonic to a square well, with walls almost impenetrable to magnons. This is the first experimental example of Bose condensation in a box. By selective rf pumping the trap can be populated with a ground-state condensate or one at any of the excited energy levels. In the latter case the ground state is simultaneously populated by relaxation from the exited level, forming a system of two coexisting condensates.