2017/12/31 by S. Autti, G. E. Volovik, V. B. Eltsov
Physics and Astronomy · #cond-mat.other
paper · pdf · doi:10.1103/physrevlett.120.215301
published as Phys. Rev. Lett. 120, 215301 (2018)
arxiv created 2018/03/30 · arxiv updated 2018/05/30
We report experimental realization of a quantum time quasicrystal, and its transformation to a quantum time crystal. We study Bose-Einstein condensation of magnons, associated with coherent spin precession, created in a flexible trap in superfluid 3He-B. Under a periodic drive with an oscillating magnetic field, the coherent spin precession is stabilized at a frequency smaller than that of the drive, demonstrating spontaneous breaking of discrete time translation symmetry. The induced precession frequency is incommensurate with the drive, and hence the obtained state is a time quasicrystal. When the drive is turned off, the self-sustained coherent precession lives a macroscopically-long time, now representing a time crystal with broken symmetry with respect to continuous time translations. Additionally, the magnon condensate manifests spin superfluidity, justifying calling the obtained state a time supersolid or a time super-crystal.