Holographic Fermi Liquids in a Spontaneously Generated Lattice
  We discuss fermions in a spontaneously generated holographic lattice background. The lattice structure at the boundary is generated by introducing a higher-derivative interaction term between a U(1) gauge field and a scalar field. We solve the equations of motion below the critical temperature at which the lattice forms, and analyze the change in the Fermi surface due to the lattice. The fermion band structure is found to exhibit a band gap due to lattice effects. 
James Alsup, Eleftherios Papantonopoulos, George Siopsis, Kubra Yeter
hep-th