Bi-Sr-Ca-Cu-O thin-film energy gap as a function of temperature and force applied to squeezable-electron-tunneling junctions

Tunneling-spectroscopy measurements have been performed on Bi-Sr-Ca-Cu-O squeezable-electron-tunneling (SET) junctions. Two distinct features have been seen in the current-voltage [I(V)] and conductance-voltage [G(V)] characteristics. One of these features has the appearance of an energy-gap signature, while the other may be due to switching to the voltage state of a grain-boundary junction that is in series with the SET junction. The latter feature can mimic the energy-gap signature in I(V) and G(V) characteristics. These two features respond very differently to changes in temperature and the force applied to the SET junctions