Quantum entanglement in the multicritical disordered Ising model

TL;DR

This paper investigates the entanglement entropy at the quantum multicritical point of the disordered transverse-field Ising model, revealing universal corner contributions and proposing a new method to locate phase transitions.

Contribution

It introduces an efficient RG method to compute entanglement entropy in disordered quantum systems and identifies universal corner contributions at the multicritical point.

Findings

Universal logarithmic corner contribution to entanglement entropy

Corner contribution acts as an entanglement susceptibility

Method to locate phase transitions using corner contributions

Abstract

Here, the entanglement entropy is calculated at the quantum multicritical point of the random transverse-field Ising model (RTIM). We use an efficient implementation of the strong disorder renormalization group method in two and three dimensions for two types of disorder. For cubic subsystems we find a universal logarithmic corner contribution to the area law b*ln(l) that is independent of the form of disorder. Our results agree qualitatively with those at the quantum critical points of the RTIM, but with new b prefactors due to having both geometric and quantum fluctuations at play. By studying the vicinity of the multicritical point, we demonstrate that the corner contribution serves as an `entanglement susceptibility', a useful tool to locate the phase transition and to measure the correlation length critical exponents.