Parafermion excitations in superfluid of quasi-molecular chains

Abstract

We study a quantum phase transition in a system of dipoles confined in a stack of $N$ identical one-dimensional lattices (tubes) polarized perpendicularly to the lattices. In this arrangement the intra-lattice interaction is purely repulsive preventing the system collapse and the inter-lattice one is attractive. The dipoles may represent polar molecules or indirect excitons. The transition separates two phases; in one of them superfluidity (understood as algebraic decay of the corresponding correlation functions) takes place in each individual lattice, in the other (chain superfluid) the order parameter is the product of bosonic operators from all lattices. We argue that in the presence of finite inter-lattice tunneling the transition belongs to the universality class of the $q=N$ two-dimensional classical Potts model. For $N=2,3,4$ the corresponding low energy field theory is the model of Z${}_N$ parafermions perturbed by the thermal operator. Results of Monte Carlo simulations are consistent with these predictions. The detection scheme for the chain superfluid of indirect excitons is outlined.

This is a significantly modified and revised version of arXiv:1203.0351 submitted to the NJP issue focused on Majorana fermions. 14 revtex pages, 7 figures. Section on detecting chains of indirect excitons is added; typos corrected

References in corpus (5)

• A High Phase-Space-Density Gas of Polar Molecules
• Ultracold dense gas of deeply bound heteronuclear molecules
• Quantum fluids of self-assembled chains of polar molecules
• Interlayer superfluidity in bilayer systems of fermionic polar molecules
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