Ground-state and thermodynamic properties of the spin-$\frac{1}{2}$ Heisenberg model on the anisotropic triangular lattice

TL;DR

This paper investigates the ground-state and thermodynamic properties of the spin-1/2 Heisenberg model on an anisotropic triangular lattice, using high-temperature series expansions and comparing results with recent experiments on a related compound.

Contribution

It introduces the entropy method for high-temperature series expansions to analyze the anisotropic triangular lattice Heisenberg model and compares findings with experimental data.

Findings

Ground-state energy matches exact diagonalization results.

Good agreement of specific heat and entropy with experiments.

Evidence supporting a gapped spin liquid phase.

Abstract

The spin-$\frac12$ triangular lattice antiferromagnetic Heisenberg model has been for a long time the prototypical model of magnetic frustration. However, only very recently this model has been proposed to be realized in the Ba$_8$CoNb$_6$O$_{24}$ compound. The ground-state and thermodynamic properties are evaluated from a high-temperature series expansions interpolation method, called "entropy method", and compared to experiments. We find a ground-state energy $e_0 = -0.5445(2)$ in perfect agreement with exact diagonalization results. We also calculate the specific heat and entropy at all temperatures, finding a good agreement with the latest experiments, and evaluate which further interactions could improve the comparison. We explore the spatially anisotropic triangular lattice and provide evidence that supports the existence of a gapped spin liquid between the square and triangular lattices.