# Colloquia

## "Stiffness from disorder in frustrated quasi-two-dimensional magnets"

**Gia-Wei Chern , Los Alamos National Lab**

[Host: Joe Poon]

Frustrated magnetism has become an extremely active field of research. The concept of geometrical frustration dates back to Wannier’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 magnets. 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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