paper

Numerical evidence for the spin-Peierls state in the frustrated quantum antiferromagnet

arXiv:cond-mat/9508002 · doi:10.1103/PhysRevB.53.2213

Abstract

We study the spin- Heisenberg antiferromagnet with an antiferromagnetic (third nearest neighbor) interaction on a square lattice. We numerically diagonalize this ``-'' model on clusters up to 32-sites and search for novel ground state properties as the frustration parameter changes. For ``larger'' we find enhancement of incommensurate spin order, in agreement with spin-wave, large- expansions, and other predictions. But for intermediate , the low lying excitation energy spectrum suggests that this incommensurate order is short-range. In the same region, the first excited state has the symmetries of the columnar dimer (spin-Peierls) state. The columnar dimer order parameter suggests the presence of long-range columnar dimer order. Hence, this spin-Peierls state is the best candidate for the ground state of the - model in an intermediate region.

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