Charge-Density-Wave-Induced Peak-Dip-Hump Structure and the Multiband Superconductivity in a Kagome Superconductor CsV${}_3$Sb${}_5$

Abstract

The entanglement of charge density wave (CDW), superconductivity, and topologically nontrivial electronic structure has recently been discovered in the kagome metal $A$V${}_3$Sb${}_5$ ($A$ = K, Rb, Cs) family. With high-resolution angle-resolved photoemission spectroscopy, we study the electronic properties of CDW and superconductivity in CsV${}_3$Sb${}_5$. The spectra around $\bar{K}$ is found to exhibit a peak-dip-hump structure associated with two separate branches of dispersion, demonstrating the isotropic CDW gap opening below $E_{\mathrm{F}}$. The peak-dip-hump lineshape is contributed by linearly dispersive Dirac bands in the lower branch and a dispersionless flat band close to $E_{\mathrm{F}}$ in the upper branch. The electronic instability via Fermi surface nesting could play a role in determining these CDW-related features. The superconducting gap of $\sim$0.4 meV is observed on both the electron band around $\bar{\Gamma }$ and the flat band around $\bar{K}$, implying the multiband superconductivity. The finite density of states (DOS) at $E_{\mathrm{F}}$ in the CDW phase are most likely in favor of the emergence of multiband superconductivity, particularly the enhanced DOS associated with the flat band. Our results not only shed light on the controversial origin of the CDW, but also offer insights into the relationship between CDW and superconductivity.

6 pages, 4 figures, PRL in press

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• Nodeless superconductivity in kagome metal CsV${}_3$Sb${}_5$ with and without time reversal symmetry breaking
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• Dynamical Study of the Origin of the Charge Density Wave in $A$V${}_3$Sb${}_5$ ($A=$K, Rb, Cs) Compounds
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• Emergence of large quantum oscillation frequencies in thin flakes of the kagome superconductor CsV${}_3$Sb${}_5$
• Spectroscopic Evidence for a Three-Dimensional Charge Density Wave in Kagome Superconductor CsV${}_3$Sb${}_5$
• Magnetic Breakdown and Topology in the Kagome Superconductor CsV3Sb5 under High Magnetic Field
• Electronic Landscape of Kagome Superconductors $\text{A}$V${}_3$Sb${}_5$ ($\text{A}$ = K, Rb, Cs) from Angle-Resolved Photoemission Spectroscopy
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• Anomalous Hall effect and two-dimensional Fermi surfaces in the charge-density-wave state of kagome metal RbV${}_3$Sb${}_5$
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• Direct Observation of Collective Modes of the Charge Density Wave in the Kagome Metal CsV${}_3$Sb${}_5$
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• Observation of anomalous amplitude modes in the kagome metal CsV${}_3$Sb${}_5$
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• Emergence of Quantum Confinement in Topological Kagome Superconductor CsV${}_3$Sb${}_5$ family
• AV${}_3$Sb${}_5$ kagome superconductors: a review with transport measurements
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• Intriguing kagome topological materials
• Electrical and thermal transport properties of kagome metals AV${}_3$Sb${}_5$ (A=K, Rb, Cs)
• Quantum Phase Transition as a Promising Route to Enhance the Critical Current in Kagome Superconductor CsV${}_3$Sb${}_5$
• Photoemission Insights to Electronic Orders in Kagome Superconductor AV3Sb5
• Local pairing versus bulk superconductivity intertwined by the charge density wave order in Cs(V${}_{1-x}$Ta${}_x$)${}_3$Sb${}_5$
• Infrared spectroscopy study of kagome material CsTi${}_3$Bi${}_5$
• Charge-density wave fluctuation driven composite order in the layered Kagome Metals
• Strongly Entangled Kondo and Kagome Lattices and the Emergent Magnetic Ground State in Heavy-Fermion Kagome Metal YbV${}_6$Sn${}_6$
• Electronic inhomogeneity in Cs- and Sb-terminated surfaces of CsV${}_3$Sb${}_5$ probed by scanning photoemission spectromicroscopy
• Current-induced magnetoresistance hysteresis in the kagome superconductor CsV${}_3$Sb${}_5$
• Enhanced Coupling of Superconductivity and Evolution of Gap Structure in CsV3Sb5 through Ta Doping
• Chern insulators and topological flat bands in cavity-embedded kagome systems
• Effective Ionic Valence and Local Magnetic Moment in Kagome Superconductors