Corner contribution to the entanglement entropy of strongly-interacting O(2) quantum critical systems in 2+1 dimensions

TL;DR

This paper confirms that the universal corner contribution to entanglement entropy in 2+1D O(2) quantum critical systems scales proportionally with the number of field components, using advanced numerical methods on different models.

Contribution

It provides the first direct numerical confirmation that the corner coefficient in entanglement entropy scales with the number of field components in strongly interacting O(N) models.

Findings

Corner coefficient is twice that of the Ising fixed point.

Universal term in entanglement entropy reflects low-energy degrees of freedom.

Results are consistent across different microscopic models.

Abstract

In a D=2+1 quantum critical system, the entanglement entropy across a boundary with a corner contains a subleading logarithmic scaling term with a universal coefficient. It has been conjectured that this coefficient is, to leading order, proportional to the number of field components N in the associated O(N) continuum $\phi^4$ field theory. Using density matrix renormalization group calculations combined with the powerful numerical linked cluster expansion technique, we confirm this scenario for the O(2) Wilson-Fisher fixed point in a striking way, through direct calculation at the quantum critical points of two very different microscopic models. The value of this corner coefficient is, to within our numerical precision, twice the coefficient of the Ising fixed point. Our results add to the growing body of evidence that this universal term in the R\'enyi entanglement entropy reflects the number of low-energy degrees of freedom in a system, even for strongly interacting theories.