Point contact tunneling spectroscopy of a Tl2Ba2CaCu2O8 thin film

Point contact tunneling spectroscopy was used to investigate the superconducting gap of Tl$_{2}$Ba$_{2}$CaCu$_{2}$O$_{8}$ (Tl- 2212 cuprate) c-axis oriented thin film of near-optimal doping, with T$_{C} $~=~106~K. The quasiparticle peaks were observed at various bias voltages in the range 30-55 mV, and the 2{\_}/k$_{B}$T$_{c}$ ratio coming from our measurement is $\sim $ 6.6-12. This is the first observation of large energy gap in near-optimally doped Tl-2212 by electron tunneling. The largest values match those found in the~infrared response and Raman scattering on Tl- 2212 (single crystals and oriented thin films) published by other groups. We discuss this in the context of experiments done by relevant techniques on related materials, the Tl-2201, Tl-2223 and Bi-2212 cuprates.