We study the zero-temperature ground-state (gs) phase diagram of the spin-12 anisotropic planar pyrochlore (or crossed chain) model using the coupled cluster method (CCM). The model is equivalently described as a frustrated J 1-J 2 antiferromagnet on the two-dimensional checkerboard lattice, with nearest-neighbor exchange bonds of strength J 10 and next-nearest-neighbor bonds of strength J 2 κJ 10. Using various antiferromagnetic (AFM) classical ground states as CCM reference states, we present results for the gs energy, average local on-site magnetization, and the susceptibilities of these states against the formation of plaquette valence-bond crystal (PVBC) and crossed-dimer valence-bond crystal (CDVBC) ordering. We show that the AFM quasiclassical state with Néel ordering is the gs phase for κ<κ c1 0.80±0.01, but that none of the infinitely degenerate set of AFM states that form the gs phase for the classical version (s→) of the model (for κ1) survive the quantum fluctuations to form a stable magnetically ordered gs phase for the s=1/2 case. Instead, our calculations indicate a PVBC-ordered phase for κ c1<κ<κ c2 1.22±0.02, and a CDVBC-ordered phase for all κκ c2. Both transitions are likely to be direct ones, although we cannot exclude very narrow coexistence regions confined to 0.79κ 0.81 and 1.20κ 1.22, respectively.
|Original language||English (US)|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|State||Published - May 11 2012|