Tunneling Spectroscopy of Tl2Ba2CuO6

Abstract

New results from tunneling spectroscopies on near optimally-doped single crystals of Tl_{2}Ba_{2}CuO_{6} (Tl-2201) junctions are presented. The superconductor-insulator-normal metal (SIN) tunnel junctions are obtained using the point-contact technique with a Au tip. The tunneling conductances reproducibly show a sharp cusp-like subgap, prominent quasiparticle peaks with a consistent asymmetry, and weakly decreasing backgrounds. A rigorous analysis of the SIN tunneling data is performed using two different models for the $d_{x^{2}-y^{2}}$ (d-wave) density of states (DOS). Based on these and earlier results, the tunneling DOS of Tl-2201 have exhibited the most reproducible data that are consistent with a d-wave gap symmetry. We show that the dip feature at $2\Delta$ that is clearly seen in SIN tunneling data of Bi_{2}Sr_{2}CaCu_{2}O_{8+\delta} is also present in Tl-2201, but at a weaker level. The gap values for crystals with a bulk T_c = 86 K are in the range of 19-25 meV.