Quantum Antiferromagnet at Finite Temperature: A Gauge Field Approach

TL;DR

This paper uses a gauge field approach to analyze the finite-temperature behavior of a quantum antiferromagnet, revealing that collective excitations dominate and one-particle excitations vanish, with implications for susceptibility and fluctuation effects.

Contribution

It introduces a gauge field framework to study the thermally disordered phase of quantum antiferromagnets, highlighting the suppression of one-particle excitations and the importance of collective modes.

Findings

One-particle excitations are suppressed at finite temperature.

Collective spin-1 excitations dominate the system's behavior.

Massive fluctuations significantly affect susceptibility calculations.

Abstract

Starting from the $CP^{N-1}$ model description of the thermally disordred phase of the $D=2$ quantum antiferromagnet, we examine the interaction of the Schwinger-boson spin-1/2 mean-field excitations with the generated gauge (chirality) fluctuations in the framework of the 1/N expansion. This interaction dramatically supresses the one-particle motion, but enhances the staggered static susceptibility. This means that actual excitations in the system are represented by the collective spin-1 excitations, whereas one-particle excitations disappear from the problem. We also show that massive fluctuations of the constraint field are significant for the susceptibility calculations. A connection with the problem of a particle in random magnetic field is discussed.