Site-selective observation of spin dynamics of a Tomonaga-Luttinger liquid in frustrated Heisenberg chains

TL;DR

This study uses $^{35}$Cl NMR to explore spin dynamics in a frustrated Heisenberg chain, revealing site-dependent Luttinger liquid behavior, anisotropic relaxation rates, and incommensurate magnetic order.

Contribution

It provides the first site-selective observation of spin dynamics in a frustrated Tomonaga-Luttinger liquid, highlighting the effects of spin-orbit coupling and incommensurate order.

Findings

Luttinger parameter varies with site due to form factor effects

Strong anisotropy in relaxation rates indicates significant spin-orbit coupling

Ground state shows incommensurate antiferromagnetic order

Abstract

Low-energy spin dynamics is investigated by $^{35}$ Cl NMR measurements in a frustrated antiferromagnet Ca$_3$ReO$_5$Cl$_2$. The local spin susceptibility measured with the Knight shift behaves as a one-dimensional Heisenberg antiferromagnet and remains constant down to low temperatures, as expected in a gapless Tomonaga-Luttinger liquid. The nuclear spin-lattice relaxation rate $T_1^{-1}$ demonstrates a slowing down of atomic motions and a power-law evolution of spin correlation. The Luttinger parameter is enhanced in a site-selective manner depending on the form factor of dynamical spin susceptibility. The strong anisotropy of $T_1^{-1}$ reflects the strong spin-orbit coupling through Dzyaloshinskii-Moriya interaction. The ground state exhibits an incommensurate antiferromagnetic ordering with low-lying magnon excitations.