Orbital-Selective High-Temperature Cooper Pairing Developed in the Two-Dimensional Limit

• Published in: arXiv.org
• Main Authors: Liu, Chaofei, Kreisel, Andreas, Zhong, Shan, Li, Yu, Andersen, Brian M, Hirschfeld, P J, Wang, Jian
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 01.12.2021
• Subjects: Electron spin; Elementary excitations; High temperature superconductors; Holes (electron deficiencies); Iron; Nesting; Physics - Materials Science; Physics - Mesoscale and Nanoscale Physics; Physics - Strongly Correlated Electrons; Physics - Superconductivity; Selectivity; Strontium titanates; Unit cell
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2112.00383

The orbital multiplicity in multiband superconductors yields orbital differentiation in normal-state properties, and can lead to orbital-selective spin-fluctuation Cooper pairing. This phenomenon has become increasingly pivotal in clarifying the pairing 'enigma' particularly for multiband high-temperature superconductors. In one-unit-cell (1-UC) FeSe/SrTiO3, the thinnest and highest-Tc member of iron-based superconductors, the standard electron-hole Fermi pocket nesting scenario is apparently not applicable since the Gamma-centered hole pockets are absent, so the actual pairing mechanism is the subject of intense debate. Here, by measuring high-resolution Bogoliubov quasiparticle interference, we report observations of highly anisotropic magnetic Cooper pairing in 1-UC FeSe. From a theoretical point of view, it is important to incorporate effects of electronic correlations within a spin-fluctuation pairing calculation, where the dxy orbital becomes coherence-suppressed. The resulting pairing gap is compatible with the experimental findings, which suggests that high-Tc Cooper pairing with orbital selectivity applies to 1-UC FeSe. Our findings imply the general existence of orbital selectivity in iron-based superconductors and the universal importance of electron correlations in high-Tc superconductors.