Holographic entanglement entropy probe on spontaneous symmetry breaking with vector order

TL;DR

This paper investigates holographic entanglement entropy in a 5D charged black brane system undergoing a phase transition, revealing critical scaling behavior and proposing a new order parameter related to vector order, with implications for understanding symmetry breaking.

Contribution

It provides analytic solutions for entanglement entropy near a phase transition in a holographic model with vector order, introducing a new order parameter and confirming the first law of entanglement entropy at criticality.

Findings

Entanglement entropy exhibits a scaling law with critical exponent β=1 near the transition.

A new order parameter O_{12} effectively distinguishes isotropic and anisotropic phases.

The first law of entanglement entropy holds even near the critical point.

Abstract

We study holographic entanglement entropy in 5-dimensional charged black brane geometry obtained from Einstein-SU(2)Yang-Mills theory defined in asymptotically AdS space. This gravity system undergoes second order phase transition near its critical point affected by a spatial component of the Yang-Mills fields, which is normalizable mode of the solution. This is known as phase transition between isotropic and anisotropic phases. We get analytic solutions of holographic entanglement entropies by utilizing the solution of bulk spacetime geometry given in arXiv:1109.4592, where we consider subsystems defined on AdS boundary of which shapes are wide and thin slabs and a cylinder. It turns out that the entanglement entropies near the critical point shows scaling behavior such that for both of the slabs and cylinder, $\Delta_\varepsilon S\sim\left(1-\frac{T}{T_c}\right)^\beta$ and the critical exponent $\beta=1$, where $\Delta_\varepsilon S\equiv S^{iso}-S^{aniso}$, and $S^{iso}$ denotes the entanglement entropy in isotropic phase whereas $S^{aniso}$ denotes that in anisotropic phase. We suggest a quantity $O_{12}\equiv S_1-S_2$ as a new order parameter near the critical point, where $S_1$ is entanglement entropy when the slab is perpendicular to the direction of the vector order whereas $S_2$ is that when the slab is parallel to the vector order. $O_{12}=0$ in isotropic phase but in anisotropic phase, the order parameter becomes non-zero showing the same scaling behavior. Finally, we show that even near the critical point, the first law of entanglement entropy is hold. Especially, we find that the entanglement temperature for the cylinder is $\mathcal T_{cy}=\frac{c_{ent}}{a}$, where $c_{ent}=0.163004\pm0.000001$ and $a$ is the radius of the cylinder.