Prof. Nic Shannon iUniversity of Bristolj

"Supersolid phases in a realistic three-dimensional spin model"

Supersolid phases, in which a superfluid component coexists with conventional
crystalline long range order, have recently attracted a great deal of attention
in the context of both solid helium and quantum spin systems. Motivated by
recent experiments on 2H-AgNiO2 [1,2], we study the magnetic phase diagram of
a realistic three-dimensional spin model with single-ion anisotropy and
competing interactions on a layered triangular lattice, using classical Monte
Carlo simulation techniques, complemented by spin-wave calculations. For
parameters relevant to experiment, we find a cascade of different phases
as a function of magnetic field, including three phases which are supersolids
in the sense of Liu and Fisher. One of these phases is continuously connected
with the collinear ground state of AgNiO2, and is accessible at relatively
low values of magnetic field. The nature of this low-field transition, and the
possibility of observing this new supersolid phase in AgNiO2, are discussed [3].

[1] E. M. Wheeler et al., Phys. Rev. B 79, 104421 (2009)

[2] A. Coldea et al., arXiv:0908.4169v1.

[3] Luis Seabra and Nic Shannon, Phys. Rev. Lett. 104, 237205 (2010)