Andreev Edge State on Semi-Infinite Triangular Lattice: Detecting the   Pairing Symmetry in Na_0.35CoO_2.yH_2O
  We study the Andreev edge state on the semi-infinite triangular lattice with different pairing symmetries and boundary topologies. We find a rich phase diagram of zero energy Andreev edge states that is a unique fingerprint of each of the possible pairing symmetries. We propose to pin down the pairing symmetry in recently discovered Na_xCoO_2 material by the Fourier-transformed scanning tunneling spectroscopy for the edge state. A surprisingly rich phase diagram is found and explained by a general gauge argument and mapping to 1D tight-binding model. Extensions of this work are discussed at the end. 
T. Pereg-Barnea and Hsiu-Hau Lin