STM/STS Study on 4a X 4a Electronic Charge Order and Inhomogeneous Pairing Gap in Superconducting Bi2Sr2CaCu2O8+d

TL;DR

This study uses STM/STS to investigate the 4a x 4a charge order and inhomogeneous pairing gaps in underdoped Bi2Sr2CaCu2O8+d, revealing their coexistence and doping dependence in the superconducting state.

Contribution

It provides new insights into the spatial coexistence of charge order and pairing gap in high-Tc cuprates, highlighting the dynamical nature of charge order and its pinning effects.

Findings

Charge order appears within the pairing gap.

Lower doping favors the charge order.

Pinned charge order correlates with inhomogeneous gaps.

Abstract

We performed STM/STS measurements on underdoped Bi2212 crystals with doping levels p ~ 0.11, ~ 0.13 and ~ 0.14 to examine the nature of the nondispersive 4a X 4a charge order in the superconducting state at T << Tc. The charge order appears conspicuously within the pairing gap, and low doping tends to favor the charge order. We point out the possibility that the 4a X 4a charge order will be dynamical in itself, and pinned down over regions with effective pinning centers. The pinned 4a X 4a charge order is closely related to the spatially inhomogeneous pairing gap structure, which has often been reported in STS measurements on high-Tc cuprates.