Abstract
Determining the types of superconducting order in quantum materials is a challenge. This is especially true when several degrees of freedom contribute to the fermiology and when superconductivity competes with other symmetry-breaking orders. One example is the kagome-lattice superconductor CsV3Sb5, in which multiband superconductivity coexists with a charge order that substantially reduces the space group symmetries of the compound. Here we demonstrate the presence of two superconducting regimes in CsV3Sb5 that are characterized by distinct transport and thermodynamic properties. Our results reveal a substantial quasiparticle weight in a high-temperature regime. At lower temperatures, this weight is removed through the formation of a second gap. We argue that the band with a gap opening at lower temperatures continues to host low-energy quasiparticles, possibly due to the nodal structure of the gap. Taken together, our results present evidence for band-selective superconductivity with uncoupled superconducting gaps.
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Acknowledgements
M.Z.H.’s group acknowledges primary support from the US Department of Energy, Office of Science, National Quantum Information Science Research Centers, the Quantum Science Center (at ORNL) and Princeton University; STM and transport instrumentation support from the Gordon and Betty Moore Foundation (Grant No. GBMF9461); and support from the US DOE under the Basic Energy Sciences programme (Grant No. DOE/BES DE-FG-02-05ER46200) for the theoretical work and sample characterization, including ARPES. M.Z.H. acknowledges partial support from the US DOE under the Basic Energy Sciences programme (grant number DOE/BES DE-FG-02-05ER46200) for the sample characterization based on advanced spectroscopy work. Sample growth was supported by the National Key Research and Development Program of China (Grant Nos. 2020YFA0308800 and 2022YFA1403400), the National Science Foundation of China (Grant No. 92065109) and the Beijing Natural Science Foundation (Grant Nos Z210006 and Z190006). Z.W. thanks the Analysis and Testing Center at BIT for assistance with facility support. L.B. is supported by DOE-BES (Award DE-SC0002613). The National High Magnetic Field Laboratory (NHMFL) acknowledges support from the US-NSF Cooperative agreement (Grant No. DMR-DMR-2128556) and the state of Florida. We thank T. Murphy, G. Jones, L. Jiao, D. Graf and R. Nowell at NHMFL for technical support. B.L. and M.H.F. are supported by the Swiss National Science Foundation (SNSF) through Division II (number 207908). B.L. additionally acknowledges funding from the Forschungskredit of the University of Zurich (Grant Nr. FK-24-090).
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The electrical transport experiments were performed by M.S.H. and Q.Z. The thermal transport work was performed by E.S.C., M.S.H. and Q.Z. The heat capacity measurements were performed by D.R. in consultation with A.F.B. and L.B. Crystals were grown by Y.L., J.L., Z.W. and Y.Y. The theoretical calculations were performed by B.L., M.H.F. and T.N. Figure development and writing of the paper were undertaken by M.S.H., L.B., M.H.F., T.N. and M.Z.H. M.Z.H. supervised the project. All authors discussed the results, interpretation and conclusion.
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Hossain, M.S., Zhang, Q., Choi, E.S. et al. Unconventional gapping behaviour in a kagome superconductor. Nat. Phys. 21, 556–563 (2025). https://doi.org/10.1038/s41567-024-02770-z
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DOI: https://doi.org/10.1038/s41567-024-02770-z
