Tomonaga-Luttinger Liquid in a Quasi-One-Dimensional S=1 Antiferromagnet Observed by the Specific Heat

TL;DR

This study provides experimental evidence for Tomonaga-Luttinger liquid behavior in a quasi-one-dimensional S=1 antiferromagnet through specific heat measurements, confirming theoretical predictions.

Contribution

First experimental observation of Tomonaga-Luttinger liquid in a quasi-one-dimensional S=1 antiferromagnet using specific heat data.

Findings

Magnetic specific heat is proportional to temperature above the critical field.

The ratio C_mag/T increases as the magnetic field approaches H_c.

Data agrees with c=1 conformal field theory predictions.

Abstract

Specific heat experiments on single crystals of the S=1 quasi-one-dimensional bond-alternating antiferromagnet Ni(C_9H_24N_4)(NO_2)ClO_4, alias NTENP, have been performed in magnetic fields applied both parallel and perpendicular to the spin chains. We have found for the parallel field configuration that the magnetic specific heat (C_mag) is proportional to temperature (T) above a critical field H_c, at which the energy gap vanishes, in a temperature region above that of the long-range ordered state. The ratio C_mag/T increases as the magnetic field approaches H_c from above. The data are in good quantitative agreement with the prediction of the c=1 conformal field theory in conjunction with the velocity of the excitations calculated by a numerical diagonalization, providing a conclusive evidence for a Tomonaga-Luttinger liquid.