In-plane thermal conductivity of Nd2CuO4:: Evidence for magnon heat transport -: art. no. 146601

We report the temperature and magnetic field dependence of the in-plane thermal conductivity (kappa(ab)) of high-quality monocrystalline Nd2CuO4. Isothermal measurements of the field dependence of kappa(ab) at low temperatures (2 Kless than or equal toTless than or equal to5 K) show no change in kappa(ab) below a critical magnetic field H-c (H(c)approximate to4.5 T for Hparallel to[100]) and H(c)approximate to2.5 T for Happroximate toparallel to[110]). Above H-c, kappa(ab) more than doubles as H is increased to 9 T. At H-c, there is a transition from a noncollinear to a collinear arrangement of the Nd and Cu spins and a collapse of the gap, Delta, in an acoustic magnon branch at k=0. Closure of this gap appears to allow the conduction of substantial amounts of heat by acoustic magnons.