STM/STS Study on 4a X 4a Electronic Charge Order of Superconducting Bi2Sr2CaCu2O8+d

TL;DR

This study uses STM to investigate a 4a x 4a electronic charge order in underdoped Bi2Sr2CaCu2O8+d, revealing its characteristics and dependence on doping and gap states, contributing to understanding high-Tc cuprate electronic structures.

Contribution

It provides detailed STM evidence of a nondispersive 4a x 4a charge order in underdoped Bi2212, clarifying its relation to the pseudogap and superconducting states.

Findings

The 4a x 4a superstructure is oriented along Cu-O bonds.

It is more intense in samples with a zero temperature pseudogap.

The superstructure is observed within the energy gaps and diminishes outside them.

Abstract

We performed low-bias STM measurements on underdoped Bi2212 crystals, and confirmed that a two-dimensional (2D) superstructure with a periodicity of four lattice constants (4a) is formed within the Cu-O plane at T<Tc. This 4a X 4a superstructure, oriented along the Cu-O bonding direction, is nondispersive and more intense in lightly doped samples with a zero temperature pseudogap (ZTPG) than in samples with a d-wave gap. The nondispersive 4a X 4a superstructure was clearly observed within the ZTPG or d-wave gap, while it tended to fade out outside the gaps. The present results provide a useful test for various models proposed for an electronic order hidden in the underdoped region of high-Tc cuprates.