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

TL;DR

This study uses angle-resolved photoemission spectroscopy to analyze the doping and temperature dependence of the pseudogap and superconducting gap in La2-xSrxCuO4, revealing universal and material-dependent two-gap behaviors.

Contribution

It demonstrates that the pseudogap and its associated temperature scale are material-independent, while the superconducting gap varies with material, highlighting different origins for these gaps.

Findings

Identification of two distinct energy and temperature scales in La2-xSrxCuO4.

The pseudogap magnitude and temperature are similar across different cuprates.

The superconducting gap magnitude varies with material, indicating different underlying mechanisms.

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 ($\pi$,0) of magnitude $\Delta^*$ and the gap around the node characterized by the d-wave order parameter $\Delta_0$, like the double-layer cuprate Bi2212. In comparison with Bi2212 having higher $T_c$'s, $\Delta_0$ is smaller, while $\Delta^*$ and $T^*$ are similar. This result suggests that $\Delta^*$ and $T^*$ are approximately material-independent properties of a single CuO$_2$ plane, in contrast the material-dependent $\Delta_0$, representing the pairing strength.