The D3-probe-D7 brane holographic fractional topological insulator
  The D3-probe-D7 brane system, oriented so as to have 2+1-dimensional Poincare symmetry, is argued to be the holographic representation of a strongly correlated fractional topological insulator which exhibits a zero-field quantized Hall effect with half-units of Hall conductivity. The phase diagram of the system with charge density and external magnetic field is found and, as well as charge gapped quantum Hall states, it exhibits metallic and semi-metallic phases with interesting behaviours. The relationship of this to other models of fractional topological insulators is discussed. 
Charlotte Kristjansen (Bohr Inst., Copenhagen U.) and Gordon W.   Semenoff (British Columbia U.)
hep-th cond-mat.str-el