Inhomogeneous spin excitations in weakly coupled spin-1/2 chains

TL;DR

This study investigates the magnetic excitations and phase transitions in the quasi-1D spin-1/2 magnet SrCo2V2O8 using neutron scattering, revealing inhomogeneous spin excitations and a transition from Neel order to a TLL state under magnetic field.

Contribution

It provides the first detailed observation of inhomogeneous spin excitations and the coexistence of Neel and TLL phases in SrCo2V2O8, highlighting local quantum phase transitions.

Findings

Discovery of two new spin excitations inside the gapped region.

Partial destabilization and complete suppression of Neel order under magnetic field.

Identification of a local quantum phase transition leading to TLL state.

Abstract

We present a systematic inelastic neutron scattering and neutron diffraction study of the magnetic structure of the quasi-1D spin-1/2 magnet SrCo2V2O8, where the interchain coupling in the Neel-type antiferromagnetic ground state breaks the static spin lattice into two independent domains. At zero magnetic field, we observe two new spin excitations with small spectral weights inside the gapped region defined by the spinon bound states. In an external magnetic field along the chain axis, the Neel order is partially destabilized above 2 T and completely suppressed at 3.9 T, above which a quantum disordered Tomonaga-Luttinger liquid (TLL) prevails. We propose that the two new modes at zero field are spinon excitations inside the domain walls. Since they have a smaller gap than those excited in the Neel domains, the underlying spin chains enter the TLL state via a local quantum phase transition at 2 T, making a stable Neel / TLL coexistence until the excitation gap closes in the Neel state at 3.9 T.