Using magnetic dynamics to measure the spin gap in a candidate Kitaev material

TL;DR

This study demonstrates that time-resolved resonant elastic x-ray scattering (tr-REXS) can effectively measure the low-energy spin gap in Kitaev candidate materials, providing insights into their spin dynamics relevant for quantum computing.

Contribution

The paper introduces the use of tr-REXS to measure the spin gap in a Kitaev candidate material, showing its effectiveness where traditional methods struggle.

Findings

Slow spin dynamics with nanosecond recovery timescales

Spin gap estimated at approximately 1 microelectronvolt

tr-REXS aligns with DMRG simulation results

Abstract

Materials potentially hosting Kitaev spin-liquid states are considered crucial for realizing topological quantum computing. However, the intricate nature of spin interactions within these materials complicates the precise measurement of low-energy spin excitations indicative of fractionalized excitations. Using Na$_{2}$Co$_2$TeO$_{6}$ as an example, we study these low-energy spin excitations using the time-resolved resonant elastic x-ray scattering (tr-REXS). Our observations unveil remarkably slow spin dynamics at the magnetic peak, whose recovery timescale is several nanoseconds. This timescale aligns with the extrapolated spin gap of $\sim$ 1 $\mu$eV, obtained by density matrix renormalization group (DMRG) simulations in the thermodynamic limit. The consistency demonstrates the efficacy of tr-REXS in discerning low-energy spin gaps inaccessible to conventional spectroscopic techniques.