Anisotropy-induced soliton excitation in magnetized strong-rung spin ladders

TL;DR

This study combines experimental electron spin resonance and theoretical analysis to reveal anisotropy-induced soliton excitations in a magnetized strong-rung spin ladder, highlighting novel low-energy dynamics in the spin liquid regime.

Contribution

It demonstrates that Dzyaloshinskii-Moriya interactions induce solitonic excitations in a well-studied spin ladder material under magnetic fields.

Findings

Orientation-dependent spin gap observed near half-magnetization.

Anomalous g-factor values detected in ESR measurements.

Solitonic excitations explained by field theoretical analysis.

Abstract

We report low temperature electron spin resonance experimental and theoretical studies of an archetype $S=1/2$ strong-rung spin ladder material (C$_{5}$H$_{12}$N)$_{2}$CuBr$_{4}$. Unexpected dynamics is detected deep in the Tomonaga-Luttinger spin liquid regime. Close to the point where the system is half-magnetized (and believed to be equivalent to a gapless easy plane chain in zero field) we observed orientation-dependent spin gap and anomalous $g$-factor values. Field theoretical analysis demonstrates that the observed low-energy excitation modes in magnetized (C$_{5}$H$_{12}$N)$_{2}$CuBr$_{4}$ are solitonic excitations caused by Dzyaloshinskii-Moriya interaction presence.