Two-gap feature in optimally electron-doped cuprates

The dependence of the Hall conductivity on temperature and magnetic field in optimally doped La2-xCexCuO4±δ (x=0.105) thin films demonstrates that both the hole and the electron bands undergo Cooper pairing. The magnetic field suppresses the dominant hole band pairing more effectively, making the subdominant electron band pairing visible. Positively charged Cooper pairs dominate the Hall signal in the mixed state at a weak magnetic field near Tc, while at large field the negatively charged Cooper pairs take over. Sign reversals of the Hall conductivity induced by superconducting fluctuation occur in the transition and can be explained by a weakly coupled two-band Ginzburg-Landau-Lawrence-Doniach model.