Long-lived coherent spin precession of 3He−B at low temperatures around 0.2Tc 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.
- Ecited levels
- Ground states
- Magnon Bose-Einstein Condenssates
Autti, S., Bunkov, Y. M., Eltsov, V. B., Heikkinen, P. J., Hosio, J. J., Hunger, P., ... Volovik, G. E. (2012). Self-trapping of magnon Bose-Einstein Condensates in the ground state and on excited levels: from harmonic to box confinement. Physical Review Letters, 108(14), 1-5. . https://doi.org/10.1103/PhysRevLett.108.145303