title: Columnar order and Ashkin-Teller criticality in mixtures of hard squares and dimers.
abstract: We show that critical exponents of the transition to columnar order in a mixture of 2×1 dimers and 2×2 hard squares on the square lattice depends on the composition of the mixture in exactly the manner predicted by the theory of Ashkin-Teller criticality, including in the hard-square limit. This result settles the question regarding the nature of the transition in the hard-square lattice gas. It also provides the first example of a polydisperse system whose critical properties depend on composition. Our ideas also lead to some interesting predictions for a class of frustrated quantum magnets that exhibit columnar ordering of the bond energies at low temperature.
authors.affiliation: Laboratoire de Physique Théorique et Modèles Statistiques, UMR 8626, Université Paris-Sud 11 and CNRS, Bâtiment 100, Orsay F-91405, France.
authors.forename: Kabir
authors.initials: K
authors.lastname: Ramola
authors.affiliation: Tata Institute of Fundamental Research, 1 Homi Bhabha Road, Mumbai, India 400005.
authors.forename: Kedar
authors.initials: K
authors.lastname: Damle
authors.affiliation: Tata Institute of Fundamental Research, 1 Homi Bhabha Road, Mumbai, India 400005.
authors.forename: Deepak
authors.initials: D
authors.lastname: Dhar