High-field quantum disordered state in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>α</mml:mi><mml:mo>−</mml:mo><mml:msub><mml:mi>RuCl</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math>: Spin flips, bound states, and multiparticle continuum
Anuja Sahasrabudhe, David A. S. Kaib, S. Reschke, Raphael German, T. C. Koethe, Jonathan Buhot, D. Kamenskyi, Ciarán Hickey, P. Becker, V. Tsurkan, A. Loidl, Seung-Hwan Do, Kwang‐Yong Choi, M. Grüninger, Stephen M. Winter, Zhe Wang, Roser Valentí, P. H. M. van Loosdrecht
Abstract
Raman and terahertz spectroscopy, combined with exact diagonalization studies, reveal the nature of the high-field phase of the proximate Kitaev material $\ensuremath{\alpha}$-RuCl${}_{3}$ as a partially polarized quantum disordered state. The state 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 low energy. The results underline the unusual nature of the high-field phase, and the important role of Kitaev and off-diagonal interactions in $\ensuremath{\alpha}$-RuCl${}_{3}$.