Eigenstate Entanglement Entropy in Random Quadratic Hamiltonians
Abstract
The eigenstate entanglement entropy has been recently shown to be a powerful tool to distinguish integrable from generic quantum-chaotic models. In integrable models, a unique feature of the average eigenstate entanglement entropy (over all Hamiltonian eigenstates) is that the volume-law coefficient depends on the subsystem fraction. Hence, it deviates from the maximal (subsystem fraction independent) value encountered in quantum-chaotic models. Using random matrix theory for quadratic Hamiltonians, we obtain a closed-form expression for the average eigenstate entanglement entropy as a function of the subsystem fraction. We test its correctness against numerical results for the quadratic Sachdev-Ye-Kitaev model. We also show that it describes the average entanglement entropy of eigenstates of the power-law random banded matrix model (in the delocalized regime), and that it is close but not the same as the result for quadratic models that exhibit localization in quasimomentum space.
Cite
@article{arxiv.2006.11302,
title = {Eigenstate Entanglement Entropy in Random Quadratic Hamiltonians},
author = {Patrycja Łydżba and Marcos Rigol and Lev Vidmar},
journal= {arXiv preprint arXiv:2006.11302},
year = {2020}
}