期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 113, 期 31, 页码 8653-8657出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1524076113
关键词
spin liquid; frustrated magnetism; thermal transport
资金
- Yamada Science Foundation
- Toray Science Foundation
- KAKENHI from Japan Society for the Promotion of Science
- KAKENHI [15H05852]
- Grants-in-Aid for Scientific Research [16K17742, 15K17691, 16K17743] Funding Source: KAKEN
When quantum fluctuations destroy underlying long-range ordered states, novel quantum states emerge. Spin-liquid (SL) states of frustrated quantum antiferromagnets, in which highly correlated spins fluctuate down to very low temperatures, are prominent examples of such quantum states. SL states often exhibit exotic physical properties, but the precise nature of the elementary excitations behind such phenomena remains entirely elusive. Here, we use thermal Hall measurements that can capture the unexplored property of the elementary excitations in SL states, and report the observation of anomalous excitations that may unveil the unique features of the SL state. Our principal finding is a negative thermal Hall conductivity kappa(xy) which the charge-neutral spin excitations in a gapless SL state of the 2D kagome insulator volborthite Cu3V2O7(OH)(2).2H(2)O exhibit, in much the same way in which charged electrons show the conventional electric Hall effect. We find that kappa(xy) is absent in the high-temperature paramagnetic state and develops upon entering the SL state in accordance with the growth of the short-range spin correlations, demonstrating that kappa(xy) is a key signature of the elementary excitation formed in the SL state. These results suggest the emergence of nontrivial elementary excitations in the gapless SL state which feel the presence of fictitious magnetic flux, whose effective Lorentz force is found to be less than 1/100 of the force experienced by free electrons.
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