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 Na2Co2TeO6 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 ∼ 1 μeV, 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.
@article{arxiv.2405.03212,
title = {Using magnetic dynamics to measure the spin gap in a candidate Kitaev material},
author = {Xinyi Jiang and Qingzheng Qiu and Cheng Peng and Hoyoung Jang and Wenjie Chen and Xianghong Jin and Li Yue and Byungjune Lee and Sang-Youn Park and Minseok Kim and Hyeong-Do Kim and Xinqiang Cai and Qizhi Li and Tao Dong and Nanlin Wang and Joshua J. Turner and Yuan Li and Yao Wang and Yingying Peng},
journal= {arXiv preprint arXiv:2405.03212},
year = {2025}
}