Finite-temperature dynamical magnetic susceptibility of quasi-one-dimensional frustrated spin-1/2 Heisenberg antiferromagnets

摘要

We study the dynamical response of frustrated, quasi-one-dimensional spin-1/2Heisenberg antiferromagnets at finite temperatures. We allow for the presenceof a Dzyaloshinskii-Moriya interaction. We concentrate on a model of weaklycoupled planes of anisotropic triangular lattices. Combining exact results forthe dynamical response of one dimensional Heisenberg chains with a Random PhaseApproximation (RPA) in the frustrated interchain couplings, we calculate thedynamical susceptibility in the disordered phase. We investigate theinstability of the disordered phase to the formation of collective modes. Wefind a very weak instability to the formation of incommensurate magnetic orderand determine the ordering temperature and wave vector. We also determine theeffects of uniform magnetic fields on the ordering transition.