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High-field quantum disordered state in α−RuCl3: Spin flips, bound states, and multiparticle continuum

Sahasrabudhe, A.; Kaib, D. A. S.; Reschke, S.; German, R.; Koethe, T. C.; Buhot, J.; Kamenskyi, D.; Hickey, C.; Becker, P.; Tsurkan, V.; Loidl, A.; Do, S. H.; Choi, K. Y.; Grüninger, M.; Winter, S. M.; Wang, Z.; Valentí, R.; van Loosdrecht, P. H. M.
Layered α−RuCl3 has been discussed as a proximate Kitaev spin-liquid compound. Raman and terahertz spectroscopy of magnetic excitations confirms that the low-temperature antiferromagnetic ordered phase features a broad Raman continuum, together with two magnonlike excitations at 2.7 and 3.6 meV, respectively. The continuum strength is maximized as long-range order is suppressed by an external magnetic field. The state above the field-induced quantum phase transition around 7.5 T is characterized by a gapped multiparticle continuum out of which a two-particle bound state emerges, together with a well-defined single-particle excitation at lower energy. Exact diagonalization calculations demonstrate that Kitaev and off-diagonal exchange terms in the Fleury-Loudon operator give rise to a pronounced intensity of these features in the Raman spectra. Our Rapid Communication firmly establishes the partially polarized quantum disordered character of the high-field phase.

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Permalink: https://www.hzdr.de/publications/Publ-30940
Publ.-Id: 30940