Louis-Paul Henry, Peter C. W. Holdsworth, Frédéric Mila, Tommaso Roscilde
The ground state properties of the S=1/2 transverse-field Ising model on the
checkerboard lattice are studied using linear spin wave theory. We consider the
general case of different couplings between nearest neighbors (J1) and
next-to-nearest neighbors (J2). In zero field the system displays a large
degeneracy of the ground state, which is exponential in the system size (for
J1=J2) or in the system's linear dimensions (for J2>J1). Quantum fluctuations
induced by a transverse field are found to be unable to lift this degeneracy in
favor of a classically ordered state at the harmonic level. This remarkable
fact suggests that a quantum-disordered ground state can be instead promoted
when non-linear fluctuations are accounted for, in agreement with existing
results for the isotropic case J1=J2. Moreover spin-wave theory shows sizable
regions of instability which are further candidates for quantum-disordered
behavior.
View original:
http://arxiv.org/abs/1202.1462
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