Phase diagram of weakly coupled Heisenberg spin chains subject to a uniform Dzyaloshinskii-Moriya interaction
Abstract
Motivated by recent experiments on spin chain materials K2CuSO4Cl2 and K2CuSO4Br2, we theoretically investigate the problem of weakly coupled spin chains (chain exchange J, interchain J') subject to a staggered between chains, but uniform within a given chain, Dzyaloshinskii-Moriya (DM) interaction of magnitude D. In the experimentally relevant limit J' D J of strong DM interaction the spins on the neighboring chains are forced to rotate in opposite directions, effectively resulting in a cancelation of the interchain interaction between components of spins in the plane normal to the vector D. This has the effect of promoting two-dimensional collinear spin density wave (SDW) state, which preserves U(1) symmetry of rotations about the D-axis. We also investigate response of this interesting system to an external magnetic field h and obtain the h-D phase diagrams for the two important configurations, h D and h D.