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Thursday, May 14th 2015

1:15 pm:

Frustrated magnetism has become an extremely active field of research. The concept of geometrical frustration dates back to Wannierâ€™s 1950 study of Ising antiferromagnet on the triangular lattice. This simple system illustrates many defining characteristics of a highly frustrated magnet, including a macroscopic ground-state degeneracy and the appearance of power-law correlations without criticality. In this talk I will discuss a simple generalization of the triangular Ising model, namely, a finite number of vertically stacked triangular layers. Our extensive numerical simulations reveal a low temperature reentrance of two Berezinskii-Kosterlitz-Thouless transitions. In particular, I will discuss how short-distance spin-spin correlations can be enhanced by thermal fluctuations, a phenomenon we termed stiffness from disorder. This is a generalization of the well-known order-by-disorder mechanism in frustrated systems. I will also present an effective field theory that quantitatively describes the low-temperature physics of the multilayer triangular Ising antiferromagnet.

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