Ferromagnetic-nematic order and strongly correlated phases of fermions in optical flux lattices

Simon C. Davenport and Nigel R. Cooper
Phys. Rev. A 92, 023608 – Published 10 August 2015

Abstract

We study a model of a two-dimensional ultracold atomic gas subjected to an “optical flux lattice”: a laser configuration where Raman-dressed atoms experience a strong artificial magnetic field. This leads to a band structure of narrow energy bands with nonzero Chern numbers. We consider the case of two-level (spin-1/2) fermionic atoms in this lattice, interacting via a repulsive s-wave contact interaction. Atoms restricted to the lowest band are described by an effective model of spinless fermions with interactions that couple states in a momentum-dependent manner across the Brillouin zone; a consequence of the Raman dressing of the two spin states. We present the results of detailed exact diagonalization studies of the many-body states for a range of filling factors, ν. First, we present evidence for the existence of a phase with coupled ferromagnetic-nematic ordering, which was previously suggested by a mean-field analysis. Second, we present evidence indicating the presence of a Laughlin-like fractional quantum Hall state occurring at filling factor ν=1/3. Finally, we observe a charge-density wave state at ν=1/2, which we are able to cleanly distinguish from the Laughlin-like state by its translational symmetry breaking and relatively low participation ratio.

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  • Received 28 April 2015

DOI:https://doi.org/10.1103/PhysRevA.92.023608

©2015 American Physical Society

Authors & Affiliations

Simon C. Davenport* and Nigel R. Cooper

  • T.C.M. Group, Cavendish Laboratory, J.J. Thomson Avenue, Cambridge CB3 0HE, United Kingdom

  • *simon.davenport2@gmail.com

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Vol. 92, Iss. 2 — August 2015

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