Anomalous low-temperature specific heat of the antiferromagnetic SU(N) Heisenberg model in a field

TL;DR

This paper investigates the low-temperature specific heat of the integrable SU(N) Heisenberg model, revealing how it varies with an external field and extending known results to arbitrary N.

Contribution

It provides a calculation of the linear specific heat coefficient for the SU(N) Heisenberg model in zero and small fields, generalizing previous N=2 results to any N.

Findings

Zero-field specific heat coefficient matches conformal field theory predictions.

In-field specific heat coefficient is reduced compared to zero field.

Results extend understanding of SU(N) models beyond N=2.

Abstract

We discuss the low-temperature specific heat of the integrable SU(N)- invariant Heisenberg model in one dimension with degrees of freedom in the symmetric rank-$m$ tensor representation, especially for the antiferromagnetic coupling. It is known that the linear specific heat coefficient $\gam$ is a function of a field which breaks the SU(N) invariance of the internal degrees of freedom. We calculate the $\gam$ in a zero field and in a small field. The in-field $\gam$ is less than the zero-field $\gam$ as expected since the entropy is reduced in the ordered system. The zero-field $\gam$ is the same as the one obtained by the prediction of the critical behavior of 1D quantum spin systems via conformal field theory. This extends the previous results for N=2 to an arbitrary N.