Quantum spin liquids (QSLs) have been at the forefront of correlated electron research ever since their proposal in 1973, and the realization that they belong to the broader class of intrinsic topological orders. According to received wisdom, QSLs can arise in frustrated magnets with low spin S, where strong quantum fluctuations act to destabilize conventional, magnetically ordered states. Here, we present a Z 2 QSL ground state that appears already in the semiclassical, large-S limit. This state has both topological and symmetry-related ground-state degeneracy, and two types of gaps, a "magnetic flux" gap that scales linearly with S and an "electric charge" gap that drops exponentially in S. The magnet is the spin-S version of the spin-1/2 Kitaev honeycomb model, which has been the subject of intense studies in correlated electron systems with strong spin-orbit coupling, and in optical lattice realizations with ultracold atoms.
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We thank G. Baskaran, A. Ralko, A. Tsirlin, Y. Wan, and M. D. Schulz for fruitful discussions. Part of this work was done at the Perimeter Institute in Waterloo, which is supported by the Government of Canada through Industry Canada and by the Province of Ontario through the Ministry of Economic Development and Innovation. This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award #DE-SC0018056.
© 2018 The Author(s).