Speaker
Description
The dynamics of isolated quantum many-body systems and the resulting relaxation of subsystems constitute one of the central problems in the study of quantum many-body physics. In particular, recent studies have attempted to understand subsystem relaxation from the viewpoint of symmetry restoration. However, the influence of band structure and geometric properties of a system on symmetry restoration remains an open question.
In this study, we investigate how space-inversion symmetry is restored in the dynamics of free fermions on a honeycomb lattice by using the entanglement asymmetry (EA), which provides a quantitative measure of symmetry breaking. Specifically, we prepare as an initial state the ground state with broken inversion symmetry by introducing an energy offset $M$($\neq$ 0) between the two sublattices, and compute the time evolution of EA after a quantum quench to $M=0$.
We find that, although the post-quench Hamiltonian is inversion symmetric, the symmetry is not restored at the subsystem level. We further show that the condition for the absence of symmetry restoration is determined by the geometric properties of the subsystem. Moreover, using a semiclassical effective theory, we demonstrate that this phenomenon originates from quasiparticles associated with a flat band.