Imaging the Two Gaps of the High-TC Superconductor Pb-Bi2Sr2CuO6+x

TL;DR

This study uses temperature-dependent scanning tunneling spectroscopy to identify two distinct energy gaps in the high-Tc superconductor Pb-Bi2Sr2CuO6+x, supporting the two-gap hypothesis and clarifying previous experimental discrepancies.

Contribution

It provides direct experimental evidence for the existence of two separate energy gaps in a high-Tc superconductor, advancing understanding of the pseudogap state.

Findings

Discovery of a narrow, homogeneous gap vanishing near Tc.

Observation of a broader, inhomogeneous gap weakly dependent on temperature.

Support for the two-gap model of the pseudogap state.

Abstract

The nature of the pseudogap state, observed above the superconducting transition temperature TC in many high temperature superconductors, is the center of much debate. Recently, this discussion has focused on the number of energy gaps in these materials. Some experiments indicate a single energy gap, implying that the pseudogap is a precursor state. Others indicate two, suggesting that it is a competing or coexisting phase. Here we report on temperature dependent scanning tunneling spectroscopy of Pb-Bi2Sr2CuO6+x. We have found a new, narrow, homogeneous gap that vanishes near TC, superimposed on the typically observed, inhomogeneous, broad gap, which is only weakly temperature dependent. These results not only support the two gap picture, but also explain previously troubling differences between scanning tunneling microscopy and other experimental measurements.