Heat capacity uncovers physics of a frustrated spin tube

TL;DR

This study investigates the low-temperature specific heat of a frustrated spin tube material, revealing Tomonaga-Luttinger liquid behavior at very low temperatures and gapped magnon excitations at higher temperatures, advancing understanding of quasi-one-dimensional antiferromagnetic systems.

Contribution

The paper provides detailed experimental insights into the specific heat of a perfect spin tube, demonstrating its quantum magnetic behavior and identifying key excitations, which was not previously characterized in such detail.

Findings

Low-temperature specific heat shows Tomonaga-Luttinger liquid behavior.

A Schottky-type peak around 2 K indicates gapped magnon excitations.

The material behaves as an effective spin-3/2 antiferromagnetic Heisenberg chain.

Abstract

We report on refined experimental results concerning the low-temperature specific heat of the frustrated spin tube material [(CuCl2tachH)3Cl]Cl2. This substance turns out to be an unusually perfect spin tube system which allows to study the physics of quasi-one dimensional antiferromagnetic structures in rather general terms. An analysis of the specific heat data demonstrates that at low enough temperatures the system exhibits a Tomonaga-Luttinger liquid behavior corresponding to an effective spin-3/2 antiferromagnetic Heisenberg chain with short-range exchange interactions. On the other hand, at somewhat elevated temperatures the composite spin structure of the chain is revealed through a Schottky-type peak in the specific heat located around 2 K. We argue that the dominating contribution to the peak originates from gapped magnon-type excitations related to the internal degrees of freedom of the rung spins.