One- and Two-Triplon Spectra of a Cuprate Ladder

TL;DR

This study uses inelastic neutron scattering to analyze one- and two-triplon excitations in a cuprate ladder, revealing detailed dispersion relations, exchange constants, and a significant ring exchange interaction.

Contribution

First clear observation of two-triplon scattering in a cuprate ladder, with detailed extraction of exchange interactions and spin gap using neutron scattering.

Findings

Spin gap of 26.4 meV identified

Two-triplon scattering observed for the first time

Exchange constants Jleg=186 meV, Jrung=124 meV, and ring exchange Jcyc=31 meV determined

Abstract

We have performed inelastic neutron scattering on the near ideal spin-ladder compound La4Sr10Cu24O41, which will serve as a model system for the investigation of doped ladders. A key feature in the analysis was the separation of one-triplon and two-triplon scattering contributions due to an antiphase rung modulation. This enabled extraction of the one-triplon dispersion which has a spin gap of 26.4+/-0.3 meV, and for the first time two-triplon scattering is clearly observed. The exchange constants are determined by fitting the data to be Jleg=186 meV and Jrung=124 meV along the leg and the rung respectively. In addition to the surprisingly large difference between Jleg and Jrung a substantial ring exchange of Jcyc=31 meV was confirmed.