Spectrum of a magnetized strong-leg quantum spin ladder

TL;DR

This study uses inelastic neutron scattering and DMRG calculations to explore the spin excitation spectrum of a magnetized quantum spin ladder, revealing a fundamental change in spin dynamics and validating quantum field theory predictions.

Contribution

It provides comprehensive experimental data and theoretical validation for the spin dynamics in a magnetized quantum spin ladder across different regimes.

Findings

Observation of a change in spin dynamics between regimes

Quantitative agreement between DMRG and experiments

Validation of quantum field theoretical predictions

Abstract

Inelastic neutron scattering is used to measure the spin excitation spectrum of the Heisenberg $S=1/2$ ladder material (C$_7$H$_10$N)$_2$CuBr$_4$ in its entirety, both in the gapped spin-liquid and the magnetic field induced Tomonaga-Luttinger spin liquid regimes. A fundamental change of the spin dynamics is observed between these two regimes. DMRG calculations quantitatively reproduce and help understand the observed commensurate and incommensurate excitations. The results validate long-standing quantum field theoretical predictions, but also test the limits of that approach.