The phase-sensitivec-axis twist experiments on cuprate superconductors.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Superconductivity

Background:

• High-transition temperature cuprate superconductors like Bi2212 and Bi2201 exhibit complex phase diagrams, often influenced by pseudogap (PG) and charge-density waves (CDWs).
• The orbital symmetry of the superconducting order parameter (OP) is crucial for understanding their electronic properties, with s-wave and d$_{x^2-y^2}$-wave being primary candidates.

Purpose of the Study:

• To review phase-sensitive c-axis twist experiments and theoretical interpretations regarding the orbital symmetry of the superconducting OP in Bi2212 and Bi2201.
• To clarify the role of the pseudogap and charge-density waves in these measurements.
• To determine the dominant orbital symmetry of the superconducting OP in these materials.

Main Methods:

• Review of phase-sensitive c-axis twist experiments on Bi2212 and Bi2201.
• Analysis of theoretical interpretations of experimental data.
• Comparison with scanning tunneling spectroscopy (STS) results on Bi2212 and electron-doped cuprates.

Main Results:

• In the SC-only region of the overdoped Bi2212 phase diagram, c-axis twist experiments strongly support an orbital symmetry containing a substantial s-wave component for the superconducting OP.
• This finding is consistent across both Bi2212 and Bi2201.
• STS experiments on Bi2212 also provide evidence for an s-wave OP, further supporting these conclusions.

Conclusions:

• The superconducting order parameter in Bi2212 and Bi2201 possesses at least a substantial s-wave component.
• These findings are consistent with results from electron-doped cuprates lacking pseudogap and charge-density wave phases.
• The study clarifies the orbital symmetry of the superconducting OP in these important high-transition temperature materials.