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arXiv:2405.03212 · npj Quantum Materials

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

Xinyi Jiang, Qingzheng Qiu, Cheng Peng, Hoyoung Jang, Wenjie Chen, Xianghong Jin, Li Yue, Byungjune Lee, Sang‐Youn Park, Minseok Kim, Hyeong‐Do Kim, Xinqiang Cai, Qizhi Li, Tao Dong, Nanlin Wang, Joshua J. Turner, Yuan Li, Yao Wang, Y. Y. Peng

Published Feb 1, 2025• 1 citation
arXivHTMLPDF

Abstract

Spin-orbit entangled materials have attracted widespread interest due to the novel magnetic phenomena arising from the interplay between spin-orbit coupling and electronic correlations. However, the intricate nature of spin interactions within Kiteav materials complicates the precise measurement of low-energy spin 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 ~1 μ 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.

DOI
10.1038/s41535-025-00737-8

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Spin-orbit entangled materials have attracted widespread interest due to the novel magnetic phenomena arising from the interplay between spin-orbit coupling and electronic correlations. However, the intricate nature of spin interactions within Kiteav materials complicates the precise measurement of low-energy spin 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 ~1 μ 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.
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The spin-orbit entangled nature of the magnetic moments in Kitaev materials is expected to give rise to a quantum spin liquid (QSL) state with fractional excitations. Using resonant inelastic x-ray scattering under a magnetic field, here the authors map the excitation spectra of $\ensuremath{\beta}$-Li2{}_{2}2​IrO3{}_{3}3​. They observe a dichotomy between a magnon-like response at low energies, originating from intertwined field-induced ground states, and a multi-spinon-like continuum at higher energies, originating from pairwise excitations of long-lived Majorana fermions of the proximate QSL.