Tunable space-time crystal in room-temperature magnetodielectrics

Abstract

We report the experimental realization of a space-time crystal with tunable periodicity in time and space in the magnon Bose-Einstein Condensate (BEC), formed in a room-temperature Yttrium Iron Garnet (YIG) film by radio-frequency space-homogeneous magnetic field. The magnon BEC is prepared to have a well defined frequency and non-zero wavevector. We demonstrate how the crystalline "density" as well as the time and space textures of the resulting crystal may be tuned by varying the experimental parameters: external static magnetic field, temperature, thickness of the YIG film and power of the radio-frequency field. The proposed space-time crystals provide a new dimension for exploring dynamical phases of matter and can serve as a model nonlinear Floquet system, that brings in touch the rich fields of classical nonlinear waves, magnonics and periodically driven systems. arXiv:1811.05801v1 [cond-mat.quant-gas]

Enhancement of the Spin Pumping Effect by Magnon Confluence Process in YIG/Pt Bilayers

“…Among them one can note classical magnon dynamics effects like parametrically stimulated recovery of a microwave signal, magnon wave‐front reversal, magnetic solitons and two‐dimensional spin‐wave bullets, strain‐induced magnon effects, nonreciprocity and transformation of spin waves in ferromagnetic‐semiconductor and ferromagnetic‐multiferroic structures, and many others. Simultaneously, novel quantum macroscopic collective phenomena, such as Bose–Einstein condensation (BEC) of magnons, magnon vortices and supercurrents, as well as a space‐time crystal in the magnon BEC open new directions for the utilization of the magnon system. The large variety of the effects in magnon systems is observed due to the manifold of multi‐magnon scattering processes in combination with the inherent nonlinearity in a magnetic medium.…”

AC Josephson effect between two superfluid time crystals

“…The manifest feature of magnon quasiparticle condensation is the emergence of coherence of the precession frequency and phase [18][19][20][21][22][23][24][25] . It is important that the coherence is spontaneous and that the precession period is not influenced by the mechanism that creates the magnons.…”

Continuous time crystal from a spontaneous many-body Floquet state

“…Using a flowing atomic condensate, we have identified a particular realization of such a state, described by a dynamical phase diagram and robust against quantum fluctuations, and designed a realistic experimental scenario for its implementation. An SMBF state extends the physics of nonlinear Floquet waves [17,18] to scenarios without external periodic driving. Apart from the intrinsic conceptual interest and potential applications, an SMBF state is a particular example of a continuous time crystal.…”

“…Floquet discrete time crystals have already been successfully achieved in setups as different as diamond nitrogen-vacancy centers [12], spin chains of ions [13], dipolar crystals [14], or atom condensates [15]. A related phenomenon is the time quasicrystal observed in magnon condensates, signaled by an incommensurate periodic response to the external Floquet driving [16][17][18]. Proposals for continuous time crystals have also been made.…”