title: Phases of a triangular-lattice antiferromagnet near saturation.
abstract: We consider 2D Heisenberg antiferromagnets on a triangular lattice with spatially anisotropic interactions in a high magnetic field close to the saturation. We show that this system possesses a rich phase diagram in a field or anisotropy plane due to competition between classical and quantum orders: an incommensurate noncoplanar spiral state, which is favored classically, and a commensurate coplanar state, which is stabilized by quantum fluctuations. We show that the transformation between these two states is highly nontrivial and involves two intermediate phases--the phase with coplanar incommensurate spin order and the one with noncoplanar double-Q spiral order. The transition between the two coplanar states is of commensurate-incommensurate type, not accompanied by softening of spin-wave excitations. We show that a different sequence of transitions holds in triangular antiferromagnets with exchange anisotropy, such as Ba(3)CoSb(2)O(9).
authors.affiliation: Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84112, USA.
authors.forename: Oleg A
authors.initials: OA
authors.lastname: Starykh
authors.affiliation: Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84112, USA.
authors.forename: Wen
authors.initials: W
authors.lastname: Jin
authors.affiliation: Department of Physics, University of Wisconsin, Madison, Wisconsin 53706, USA.
authors.forename: Andrey V
authors.initials: AV
authors.lastname: Chubukov