Hilbert-space correlations beyond multifractality and bipartite entanglement in many-body localized systems
Sthitadhi Roy
Abstract
Eigenstates of many-body localized (MBL) systems are characterized by area-law bipartite entanglement along with multifractal statistics of their amplitudes on Hilbert space. At the same time, sparse random pure states with fractal statistics are not compatible with area law and necessarily exhibit volume-law entanglement. This raises the question regarding what correlation functions of Hilbert-space amplitudes MBL eigenstates must possess for their area-law entanglement to be compatible with their multifractality. In this Letter, we identify and compute such appropriate Hilbert-space correlations which carry information of entanglement. We find that, for MBL eigenstates, these correlations are qualitatively different not only from those of ergodic states but also of sparse random states with fractal statistics. This enables us to show that indeed the said correlations lie at the heart of the coexistence of area-law entanglement and multifractality for MBL eigenstates.