Local dynamics and thermal activation in the transverse-field Ising chain

TL;DR

This paper investigates the local spin dynamics of the transverse-field Ising chain at finite temperatures, revealing distinctive temperature dependencies and a thermal-activation gap in NMR relaxation rates, advancing understanding of quantum criticality.

Contribution

It uncovers the temperature-dependent local dynamics of spins in the TFIC and identifies a thermal-activation gap in NMR relaxation rates, providing new insights into quantum critical behavior.

Findings

Distinct temperature dependencies of local spin dynamics

Thermal-activation gap in NMR $1/T_2^{\

Revealed a new feature of finite-temperature dynamics in the TFIC

Abstract

There has been considerable recent progress in identifying candidate materials for the transverse-field Ising chain (TFIC), a paradigmatic model for quantum criticality. Here, we study the local spin dynamical structure factor of different spin components in the quantum disordered region of the TFIC. We show that the low-frequency local dynamics of the spins in the Ising- and transverse-field directions have strikingly distinctive temperature dependencies. This leads to the thermal-activation gap for the secular term of the NMR $1/T_2^{\prime}$ relaxation rate to be half of that for the $1/T_1$ relaxation rate. Our findings reveal a new surprise in the nonzero-temperature dynamics of the venerable TFIC model and uncover a means to evince the material realization of the TFIC universality.