Unconventional gapping behavior in a kagome superconductor

Abstract

Determining the types of superconducting order in quantum materials is a challenge, especially when multiple degrees of freedom, such as bands or orbitals, contribute to the fermiology and when superconductivity competes, intertwines, or coexists with other symmetry-breaking orders. Here, we study the Kagome-lattice superconductor CsV3Sb5, in which multiband superconductivity coexists with a charge order that substantially reduces the compound's space group symmetries. Through a combination of thermodynamic as well as electrical and thermal transport measurements, we uncover two superconducting regimes with distinct transport and thermodynamic characteristics, while finding no evidence for a phase transition separating them. Thermodynamic measurements reveal substantial quasiparticle weight in a high-temperature regime. At lower temperatures, this weight is removed via the formation of a second gap. The two regimes are sharply distinguished by a pronounced enhancement of the upper critical field at low temperatures and by a switch in the anisotropy of the longitudinal thermal conductivity as a function of in-plane magnetic field orientation. We argue that the band with a gap opening at lower temperatures continues to host low-energy quasiparticles, possibly due to a nodal structure of the gap. Taken together, our results present evidence for band-selective superconductivity with remarkable decoupling of the (two) superconducting gaps. The commonly employed multiband scenario, whereby superconductivity emerges in a primary band and is then induced in other bands appears to fail in this unconventional kagome superconductor. Instead, band-selective superconducting pairing is a paradigm that seems to unify seemingly contradicting results in this intensely studied family of materials and beyond.

Nature Physics (2024); in press

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Cited by in corpus (11)

• Kagome metals
• Thermomodulated intrinsic Josephson effect in Kagome CsV3Sb5
• Switchable chiral 2x2 pair density wave in pure CsV3Sb5
• Phase-sensitive evidence for pair density waves in a kagome superconductor
• Altermagnetism in an interacting model of Kagome materials
• Superconducting critical temperature and dimensionality tuning of RbV${}_3$Sb${}_5$ via biaxial strain
• High-throughput study of kagome compounds in the AV3Sb5 family
• Epitaxial growth and magneto-transport properties of kagome metal FeGe thin films
• Topological pair density waves in kagome superconductors
• Strain-Tuned Nodal Superconductivity in the Charge-Ordered Kagome Metal CsV${}_3$Sb${}_5$
• Electron-electron and electron-phonon collision cross sections in CsV3Sb5