Quantitative connection between the nanoscale electronic inhomogeneity and the pseudogap of Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ superconductors

TL;DR

This study establishes a quantitative link between nanoscale electronic inhomogeneity and the pseudogap phenomena in Bi$_2$Sr$_2$CaCu$_2$O$_{8+eta}$, revealing that specific coverage levels of inhomogeneity correspond to different pseudogaps and are crucial for high-temperature superconductivity.

Contribution

It introduces a hole-scale analysis connecting INSEG coverage to the two pseudogaps, providing a geometric perspective on their origin and relation to superconductivity.

Findings

50% INSEG coverage corresponds to the upper pseudogap.

100% INSEG coverage corresponds to the lower pseudogap.

INSEG and superconductivity coexist across doping levels.

Abstract

We have found a quantitative connection between the evolution of the inhomogeneous nanoscale electronic gaps (INSEG) state detected in Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ by scanning tunneling microscopy/spectroscopy (STM/S) and the two universal, the upper and the lower, pseudogaps in high-temperature cuprate superconductors (HTCS). When the doping and temperature dependent INSEG map were analyzed by using our proposed hole-scale, we find that the two pseudogaps are connected to two specific coverages of the CuO$_2$ plane by INSEG: the 50\% and 100\% coverages of the CuO$_2$ planes by INSEG correspond to the upper and lower pseudogaps, respectively. This quantitative connection to the two pseudogaps indicates that the origin of the measured pseudogap energies and temperatures are intimately related to the geometrical coverage of the CuO$_2$ planes by the INSEG state. We find that INSEG and superconductivity coexist in the underdoped to the overdoped regimes. We suggest that pseudogap states are microscopically inhomogeneous and 100\% coverage of the CuO$_2$ planes by the INSEG is a necessary condition for the high-$T_c$ superconductivity.