Complete bond-operator theory of the two-chain spin ladder

TL;DR

This paper develops a comprehensive bond-operator theory for two-chain spin ladders, enabling accurate predictions of thermodynamic properties and magnon behavior across all finite temperatures and magnetic fields.

Contribution

It introduces three qualitative advances that extend the bond-operator framework to all finite temperatures and magnetic fields in the gapped regime.

Findings

Quantitative comparison with experimental specific heat data

Predictions for thermal renormalization of triplet magnon excitations

Extended theory applicable across all finite temperatures and magnetic fields

Abstract

The discovery of the almost ideal, two-chain spin-ladder material (C_5H_12N)_2CuBr_4 has once again focused attention on this most fundamental problem in low-dimensional quantum magnetism. Within the bond-operator framework, three qualitative advances are introduced which extend the theory to all finite temperatures and magnetic fields in the gapped regime. This systematic description permits quantitative and parameter-free experimental comparisons, which are presented for the specific heat, and predictions for thermal renormalization of the triplet magnon excitations.