Continuously Doping Bi 2 Sr 2 CaCu 2 O 8+{\delta} into Electron-Doped Superconductor by CaH 2 Annealing Method

TL;DR

This paper introduces a novel CaH 2 annealing method to continuously tune the doping level of Bi2212 superconductors, enabling transition from hole to electron doping and revealing new superconducting phases.

Contribution

It is the first to apply CaH 2 annealing for doping control in Bi2212, expanding the doping range and revealing electron doping effects.

Findings

CaH 2 annealing effectively changes oxygen content in Bi2212

Transition from hole to electron doping achieved

Evidence of low-Tc superconducting phase in electron-doped regime

Abstract

As a typical hole-doped cuprate superconductor, Bi 2 Sr 2 CaCu 2 O 8+{\delta} (Bi2212) carrier doping is mostly determined by its oxygen content. Traditional doping methods can regulate its doping level within the range of hole doping. Here we report the first application of CaH 2 annealing method in regulating the doping level of Bi2212. By continuously controlling the anneal time, a series of differently doped samples can be obtained. The combined experimental results of x-ray diffraction, scanning transmission electron microscopy, resistance and Hall measurements demonstrate that the CaH 2 induced topochemical reaction can effectively change the oxygen content of Bi2212 within a very wide range, even switching from hole doping to electron doping. We also found evidence of a low-T c superconducting phase in the electron doping side.