Speaker
Description
Dynamical stabilization of nonequilibrium energy states is a topic of broad relevance to physics, mechanics, and biology. Dynamical stabilization can be achieved by coupling a system to a nonthermal bath, inducing a phase transition that drives the system out of its ground state and stabilizes a high-energy stationary state. These so-called dissipative phase transitions are much less studied than traditional ones driven, e.g., by temperature or applied fields. However, they are attracting increasing interest because they provide access to unusual states of matter, in which fluctuations of the order parameter change character across the transition, leading to drastic changes in the dynamical response function of the system. The magnetic analogue of a dissipative phase transition consists in switching the magnetization against an external field, dynamically stabilizing a uniform magnetic state with negative energy magnon excitations, so-called antimagnons. Here we use current-induced spin-orbit torques that enable spin injection across a macroscopic sample to induce dynamic stabilization of the magnetization in a Bi:YIG layer combining exceptionally low damping with nearly-compensated magnetic anisotropy [1]. This allows us to tune dissipation to the level required to reach the symmetry-breaking steady state without “killing” the nonequilibrium dynamics via positive damping. Magneto-optical Kerr effect measurements and micromagnetic simulations provide clear signatures of a dissipative phase transition leading to full inversion of the spin population, elucidating the role of nonlinear magnon scattering, magnetic field, and system’s size in dynamical stabilization of the magnetization.
[1] E. Karadza, H. Wang, P. Noël, W. Legrand, R. Schlitz, and P. Gambardella, Dynamical Stabilization of Inverted Magnetization and Antimagnons by Spin Injection in an Extended Magnetic System, arXiv:2601.09569.