Ashkin-teller criticality and pseudo-first-order behavior in a frustrated Ising model on the square lattice

• Published in: Physical review letters Vol. 108; no. 4; p. 045702
• Main Authors: Jin, Songbo, Sen, Arnab, Sandvik, Anders W
• Format: Journal Article
• Language: English
• Published: United States 24-01-2012
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/physrevlett.108.045702

We study the challenging thermal phase transition to stripe order in the frustrated square-lattice Ising model with couplings J(1) < 0 (nearest-neighbor, ferromagnetic) and J(2) > 0 (second-neighbor, antiferromagnetic) for g = J(2)/|J(1| > 1/2. Using Monte Carlo simulations and known analytical results, we demonstrate Ashkin-Teller criticality for g ≥ g*; i.e., the critical exponents vary continuously between those of the 4-state Potts model at g = g* and the Ising model for g → ∞. Thus, stripe transitions offer a route to realizing a related class of conformal field theories with conformal charge c = 1 and varying exponents. The transition is first order for g < g* = 0.67 ± 0.01, much lower than previously believed, and exhibits pseudo-first-order behavior for |g* ≤ g </~1.