Spin-charge-density wave in a rounded-square Fermi surface for ultracold atoms
Institute for Theoretical Physics Utrecht University - 3508 TD Utrecht, The Netherlands, EU
2 Joint Quantum Institute, National Institute of Standards and Technology, and University of Maryland Gaithersburg, MD, 20899, USA
Accepted: 5 January 2012
We derive and discuss an experimentally realistic model describing ultracold atoms in an optical lattice including a commensurate, but staggered, spin-flip term. The resulting band structure is quite exotic; fermions in the third band have an unusual rounded picture-frame Fermi surface (essentially two concentric squircles), leading to imperfect nesting. We develop a generalized theory describing the spin and charge degrees of freedom simultaneously at the random-field-approximation level, and show that the system can develop a coupled spin-charge-density wave order. Our generic approach can be used to study spin and charge instabilities in many materials, such as high-Tc superconductors, organic compounds, graphene, and iron pnictides.
PACS: 37.10.Jk – Atoms in optical lattices / 03.75.Ss – Degenerate Fermi gases / 67.85.-d – Ultracold gases, trapped gases
© EPLA, 2012