Giant magnetic-field dependence of the coupling between spin Tomonaga-Luttinger liquids in BaCo2V2O8

TL;DR

This study reveals a giant magnetic-field dependence of inter-chain coupling in BaCo2V2O8, leading to multiple ordered phases, explained by the interplay of coupled spin chains and incommensurate fluctuations modeled as Tomonaga-Luttinger liquids.

Contribution

It demonstrates a significant magnetic-field dependence of inter-chain coupling in a spin-chain system, linking it to incommensurate fluctuations and Tomonaga-Luttinger liquid behavior.

Findings

Three magnetically ordered phases between 3.8 T and 22.8 T

Coupling varies by a factor of 24 with magnetic field

Emergence of novel phenomena from coupled spin chains

Abstract

We use nuclear magnetic resonance to map the complete low-temperature phase diagram of the antiferromagnetic Ising-like spin-chain system BaCo2V2O8 as a function of the magnetic field applied along the chains. In contrast to the predicted crossover from the longitudinal incommensurate phase to the transverse antiferromagnetic phase, we find a sequence of three magnetically ordered phases between the critical fields 3.8 T and 22.8 T. Their origin is traced to the giant magnetic-field dependence of the total effective coupling between spin chains, extracted to vary by a factor of 24. We explain this novel phenomenon as emerging from the combination of nontrivially coupled spin chains and incommensurate spin fluctuations in the chains treated as Tomonaga-Luttinger liquids.