Universal versus Material-Dependent Two-Gap Behaviors in the High-Tc Cuprates: Angle-Resolved Photoemission Study of La2-xSrxCuO4

Abstract

We have investigated the doping and temperature dependences of the pseudogap/superconducting gap in the single-layer cuprate La${}_{2-x}$Sr${}_x$CuO${}_4$ by angle-resolved photoemission spectroscopy. The results clearly exhibit two distinct energy and temperature scales, namely, the gap around ($\ddot{I}€$,0) of magnitude $\hat{I}{”}^{\ast }$ and the gap around the node characterized by the d-wave order parameter $\hat{I}{”}_0$, like the double-layer cuprate Bi2212. In comparison with Bi2212 having higher $T_c$'s, $\hat{I}{”}_0$ is smaller, while $\hat{I}{”}^{\ast }$ and $T^{\ast }$ are similar. This result suggests that $\hat{I}{”}^{\ast }$ and $T^{\ast }$ are approximately material-independent properties of a single CuO${}_2$ plane, in contrast the material-dependent $\hat{I}{”}_0$, representing the pairing strength.

5 pages, 4 figures