Spinon continuum in the Heisenberg quantum chain compound Sr$_2$V$_3$O$_9$

TL;DR

This study investigates magnetic excitations in Sr$_2$V$_3$O$_9$, revealing a spinon continuum consistent with weakly coupled $S=1/2$ chains and confirming antiferromagnetic intrachain interactions through experimental and theoretical analysis.

Contribution

The paper provides experimental evidence of a spinon continuum in Sr$_2$V$_3$O$_9$ and validates theoretical models for weakly coupled $S=1/2$ chains.

Findings

Observation of a ~22 meV spinon continuum

Emergence of magnetic Bragg peaks near 5.3 K

Confirmation of antiferromagnetic intrachain interactions ~7.1 meV

Abstract

Magnetic excitations in the spin chain candidate Sr$_2$V$_3$O$_9$ have been investigated by inelastic neutron scattering on a single crystal sample. A spinon continuum with a bandwidth of $\sim22$ meV is observed along the chain formed by alternating magnetic V$^{4+}$ and nonmagnetic V$^{5+}$ ions. Incipient magnetic Bragg peaks due to weak ferromagnetic interchain couplings emerge when approaching the magnetic transition at $T_N\sim 5.3$ K while the excitations remain gapless within the instrumental resolution. Comparisons to the Bethe ansatz, density matrix renormalization group (DMRG) calculations, and effective field theories confirm Sr$_2$V$_3$O$_9$ as a host of weakly coupled $S = 1/2$ chains dominated by antiferromagnetic intrachain interactions of $\sim7.1$(1) meV.