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

• Published in: Nano letters Vol. 22; no. 8; pp. 3245 - 3251
• Main Authors: Liu, Chaofei, Kreisel, Andreas, Zhong, Shan, Li, Yu, Andersen, Brian M, Hirschfeld, Peter, Wang, Jian
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 27.04.2022
• Subjects: Chemistry; Materials Science; Physics; Science & Technology - Other Topics; orbital selectivity; Cooper pairing; one-unit-cell FeSe/SrTiO3; self-energy; Bogoliubov quasiparticle interference
• ISSN: 1530-6984; 1530-6992; 1530-6992
• DOI: 10.1021/acs.nanolett.1c04863

For multiband superconductors, the orbital multiplicity yields orbital differentiation in normal-state properties and can lead to orbital-selective spin-fluctuation Cooper pairing. The orbital-selective phenomenon has become increasingly pivotal in clarifying the pairing “enigma”, particularly for multiband high-temperature superconductors. Meanwhile, in one-unit-cell (1-UC) FeSe/SrTiO3, since the standard electron–hole Fermi pocket nesting scenario is inapplicable, the actual pairing mechanism is subject to intense debate. Here, by measuring high-resolution Bogoliubov quasiparticle interference, we report observations of highly anisotropic magnetic Cooper pairing in 1-UC FeSe. Theoretically, it is important to incorporate orbitally selective effects of electronic correlations within a spin-fluctuation pairing calculation, where the d xy orbital becomes coherence-suppressed. The resulting pairing gap is compatible with the experimental findings, which suggests that high-T c Cooper pairing with orbital selectivity applies to 2D-limit 1-UC FeSe. Our findings imply the general existence of orbital selectivity in iron-based superconductors and the universal significance of electron correlations in high-T c superconductors.