Competing orders, non-linear sigma models, and topological terms in quantum magnets

Senthil, T and Fisher, Matthew PA (2005) Competing orders, non-linear sigma models, and topological terms in quantum magnets. [Preprint]

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Abstract

A number of examples have demonstrated the failure of the Landau-Ginzburg-Wilson(LGW) paradigm in describing the competing phases and phase transitions of two dimensional quantum magnets. In this paper we argue that such magnets possess field theoretic descriptions in terms of their slow fluctuating orders provided certain topological terms are included in the action. These topological terms may thus be viewed as what goes wrong within the conventional LGW thinking. The field theoretic descriptions we develop are possible alternates to the popular gauge theories of such non-LGW behavior. Examples that are studied include weakly coupled quasi-one dimensional spin chains, deconfined critical points in fully two dimensional magnets, and two component massless QED3. A prominent role is played by an anisotropic O(4) non-linear sigma model in three space-time dimensions with a topological theta term. Some properties of this model are discussed. We suggest that similar sigma model descriptions might exist for fermionic algebraic spin liquid phases.

Item Type:	Preprint
Publication:	Los Alamos National Laboratory, Preprint Archive, Condensed Matter
Department/Centre:	Division of Physical & Mathematical Sciences > Physics
Date Deposited:	18 Jan 2006
Last Modified:	19 Sep 2010 04:22
URI:	http://eprints.iisc.ac.in/id/eprint/4944

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