Flat-band enhanced antiferromagnetic fluctuations and superconductivity in pressurized CsCr3Sb5

• Published in: Nature communications Vol. 16; no. 1; pp. 1375 - 8
• Main Authors: Wu, Siqi, Xu, Chenchao, Wang, Xiaoqun, Lin, Hai-Qing, Cao, Chao, Cao, Guang-Han
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 05.02.2025; Nature Publishing Group; Nature Portfolio
• Subjects: 639/766/119/1003; 639/766/119/995; Antiferromagnetism; Band theory; Condensed matter physics; Electron spin; Electrons; Ferromagnetism; First principles; Fluctuations; High pressure; Humanities and Social Sciences; multidisciplinary; Science; Science (multidisciplinary); Spin dynamics; Superconductivity
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-025-56582-7

The spin dynamics and electronic orders of the kagome system at different filling levels stand as an intriguing subject in condensed matter physics. By first-principles calculations and random phase approximation analyses, we investigate the spin fluctuations and superconducting instabilities in kagome phase of CsCr 3 Sb 5 under high pressure. At the filling level slightly below the kagome flat bands, our calculations reveal strong antiferromagnetic spin fluctuations in CsCr 3 Sb 5 , together with a leading s ± -wave and a competing ( d x y , d x 2 − y 2 )-wave superconducting order. Unlike the general intuition that the flat bands are closely related to the ferromagnetic correlations, here we propose a sublattice-momentum-coupling-driven mechanism for the antiferromagnetic fluctuations enhanced from the unoccupied flat bands. The mechanism is generally applicable to kagome systems where the Fermi level intersects near the flat bands, offering a new perspective for future studies of geometrically frustrated systems. The authors theoretically investigate the spin fluctuations and superconducting instabilities in the kagome phase of CsCr 3 Sb 5 under high pressure. They find that incipient flat bands play a role in enhancing antiferromagnetic fluctuations, which in turn mediate the competing s -wave and d -wave superconducting ordering.