A Holographic Model for Paramagnetism/antiferromagnetism Phase Transition

TL;DR

This paper develops a holographic model to describe the phase transition between paramagnetism and antiferromagnetism, capturing spontaneous magnetic ordering and responses to external magnetic fields in a black brane background.

Contribution

It introduces a novel holographic framework with two antisymmetric tensor fields to model antiferromagnetic phase transitions and magnetic responses.

Findings

Spontaneous antiparallel magnetic moment condensation at low temperatures.

Magnetic susceptibility peaks at the critical temperature, following Curie-Weiss law.

Existence of a critical magnetic field $B_c$ inducing a second order phase transition.

Abstract

In this paper we build a holographic model of paramagnetism/antiferromagnetism phase transition, which is realized by introducing two real antisymmetric tensor fields coupling to the background gauge field strength and interacting with each other in a dyonic black brane background. In the case without external magnetic field and in low temperatures, the magnetic moments condense spontaneously in antiparallel manner with the same magnitude and the time reversal symmetry is also broken spontaneously (if boundary spatial dimension is more than 2, spatial rotational symmetry is broken spontaneously as well), which leads to an antiferromagnetic phase. In the case with weak external magnetic field, the magnetic susceptibility density has a peak at the critical temperature and satisfies the Curie-Weiss law in the paramagnetic phase of antiferromagnetism. In the strong external magnetic field case, there is a critical magnetic field $B_c$ in antiferromagnetic phase: when magnetic field reaches $B_c$, the system will return into the paramagnetic phase by a second order phase transition.