Temperature dependence of the work function of Bi2Sr2CaCu2O8 single crystal cleaved at low temperature

We measured the anomalous change in the work function of Bi2Sr2CaCu2O8 around a critical temperature (Tc 85 K). The work function becomes a minimum at Tc; the work function decreases in a normal-conductive state and then increases in a superconductive state as the temperature decreases. An increase in the work function for a transition from a normal-conductive state to a superconductive state at 0 K is about 9 meV. The contribution of the chemical potential and the surface dipole barrier to the work function are discussed.