Entanglement and correlation spreading in non-Hermitian spin chains

Abstract

Non-Hermitian quantum many-body systems are attracting widespread interest for their exotic properties, including unconventional quantum criticality and topology. Here, we study how quantum information and correlations spread under a quantum quench generated by a prototypical non-Hermitian spin chain. Using the mapping to fermions, we solve exactly the problem and compute the entanglement entropy and the correlation dynamics in the thermodynamic limit. Depending on the quench parameters, we identify two dynamical phases. One is characterized by rapidly saturating entanglement and correlations. The other presents a logarithmic entanglement growth in time and correlations spreading faster than the associated unitary system, with collapses and revivals giving rise to a modulated light-cone structure. Here, in the long-time limit, we analytically compute the entanglement entropy that follows a logarithmic law, with an effective central charge that we obtain in closed form. Our results provide an example of an exactly solvable non-Hermitian many-body problem that shows rich physics, including entanglement and spectral transitions.