Semiclassical simulations predict glassy dynamics for disordered Heisenberg models

Absence of thermalization in an interacting system of thousands of quantum spins

“…1 was averaged over 100 samples of random atom positions to decrease statistical fluctuations from random couplings (see methods). The magnetization relaxes to zero slowly, following a stretched exponential law as discussed in previous work [7,38,39], and reaches a steady-state on a time scale of ∼ 10J −1 median in units of the inverse median nearest neighbor interaction strength. The steady-state value agrees with diagonal and microcanonical ensemble predictions (orange and blue hollow arrows) as all eigenstates already have vanishing x-magnetization due An external field represented by the violet arrow couples the energy levels of each spin- 1 2 particle resonantly with a field strength Ω.…”

Observation of universal relaxation dynamics in disordered quantum spin systems

“…Thus, for non-integrable models, no analytic solution exists, and it remains an open question in which manner the system relaxes after a quantum quench. Semi-classical simulations suggest that nonintegrable Heisenberg XYZ Hamiltonians present out-ofequilibrium dynamics that follow a stretched exponential law like the Ising model independent of their symmetry [27]. However, these semiclassical approximations neglect quantum effects beyond initial quantum fluctua- tions and may miss relaxation behaviors owing to large scale correlation propagation associated to build up of entanglement.…”