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

Abstract

We study a model of a 2D ultracold atomic gas subject to an "optical flux lattice": a laser configuration where Raman-dressed atoms experience a strong artificial magnetic field. This leads to a bandstructure of narrow energy bands with non-zero 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, $\nu$. 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 $\nu =1/3$. Finally, we observe a charge density wave state at $\nu =1/2$, which we are able to cleanly distinguish from the Laughlin-like state by its translational symmetry breaking and relatively small participation ratio.

7 pages, 9 figures

References in corpus (9)

• Many-Body Physics with Ultracold Gases
• High temperature fractional quantum Hall states
• Fractional quantum Hall states at zero magnetic field
• Fractional quantum Hall effect in the absence of Landau levels
• Itinerant Ferromagnetism in a Fermi Gas of Ultracold Atoms
• Optical Flux Lattices for Ultracold Atomic Gases
• Interacting bosons in topological optical flux lattices
• Fractional Quantum Hall States of Dipolar Gases in Chern Bands
• Coupled Ferromagnetic and Nematic Ordering of Fermions in an Optical Flux Lattice