We report the experimental observation of a discontinuous change in slope at T c of the temperature dependence of the work function of YBa2Cu3C>7-<5. We interpret this effect as a superconductivityinduced temperature dependence of the chemical potential. Using a general thermodynamic relation for second-order phase transitions and published values of the specific heat jump, we extract a value for d\r\T c /dn, with n the charge carrier density. This value is consistent with hole-type superconductivity.

No abstract

No abstract

Lines in YBa2Cu307 with widths down to 200 nanometers and properties comparable with the original film, have been defined using electron beam lithography and plasma etching. One predicted property of lines smaller than the magnetic penetration depth is an increase in the critical current density due to pinning of the vortices at the edge of the sample. There have been several reports of experimental observation of edge pinning in narrow YBa2Cu307 lines. We present systematic measurements of narrow lines that should be far into the edge pinning regime. Nevertheless no increase of critical current density is observed in the smallest lines.

No abstract