Stiffness from Disorder in Triangular-Lattice Ising Thin Films

Abstract

We study the triangular lattice Ising model with a finite number of vertically stacked layers and demonstrate a low temperature reentrance of two Berezinskii-Kosterlitz-Thouless transitions, which results in an extended disordered regime down to $T=0$. Numerical results are complemented with the derivation of an effective low-temperature dimer theory. Contrary to order by disorder, we present a new scenario for fluctuation-induced ordering in frustrated spin systems. While short-range spin-spin correlations are enhanced by fluctuations, quasi-long-range ordering is precluded at low enough temperatures by proliferation of topological defects.

8 pages, 8 figures; version 3; Replacement of "Reentrant Berezinskii-Kosterlitz-Thouless Transition in a Triangular Ising Thin Film" (http://arxiv.org/abs/1310.3468v2); published in Phys. Rev. Lett