2016/11/30 by Mengxing Ye, Andrey V. Chubukov
Physics and Astronomy · #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.95.014425
published as Phys. Rev. B 95, 014425 (2017) · published version
arxiv created 2017/05/23 · arxiv updated 2017/05/25
We present the zero temperature phase diagram of a Heisenberg antiferromagnet on a frustrated triangular lattice with nearest neighbor (J1) and next nearest neighbor (J2) interactions, in a magnetic field. We show that the classical model has an accidental degeneracy for all J2/J1 and all fields, but the degeneracy is lifted by quantum fluctuations. We show that at large S, for J2/J1 <1/8, quantum fluctuations select the same sequence of three sublattice co-planar states in a field as for J2 =0, and for 1/8<J2/J1 <1 they select the canted stripe state for all non-zero fields. The transition between the two states is first order in all fields, with the hysteresis width set by quantum fluctuations. We study the model with arbitrary S, including S=1/2, near the saturation field by exploring the fact that near saturation the density of bosons is small for all S. We show that for S >1, the transition remains first order, with a finite hysteresis width, but for S=1/2 and, possibly, S=1, there appears a new intermediate phase, likely without a spontaneous long-range order.