Roton pair density wave in a strong-coupling kagome superconductor

By Hui Chen, Haitao Yang, Bin Hu, Zhen Zhao, Jie Yuan, Yuqing Xing, Guojian Qian, Zihao Huang, Geng Li, Yu-xiang Ye and 13 more. Nature, 2021

618 citations recorded by the source corpus.

The transition metal kagome lattice materials host frustrated, correlated and topological quantum states of matter1–9. Recently, a new family of vanadium-based kagome metals, AV3Sb5 (A = K, Rb or Cs), with topological band structures has been discovered10,11. These layered compounds are nonmagnetic and undergo charge density wave transitions before developing superconductivity at low temperatures11–19. Here we report the observation of unconventional superconductivity and a pair density wave (PDW) in CsV3Sb5 using scanning tunnelling microscope/spectroscopy and Josephson scanning tunnelling spectroscopy. We find that CsV3Sb5 exhibits a V-shaped pairing gap Δ ~ 0.5 meV and is a strong-coupling superconductor (2Δ/kBTc ~ 5) that coexists with 4a0 unidirectional and 2a0 × 2a0 charge order. Remarkably, we discover a 3Q PDW accompanied by bidirectional 4a0/3 spatial modulations of the superconducting gap, coherence peak and gap depth in the tunnelling conductance. We term this novel quantum state a roton PDW associated with an underlying vortex–antivortex lattice that can account for the observed conductance modulations. Probing the electronic states in the vortex halo in an applied magnetic field, in strong field that suppresses superconductivity and in zero field above Tc, reveals that the PDW is a primary state responsible for an emergent pseudogap and intertwined electronic order. Our findings show striking analogies and distinctions to the phenomenology of high-Tc cuprate superconductors, and provide groundwork for understanding the microscopic origin of correlated electronic states and superconductivity in vanadium-based kagome metals. A study reports unconventional superconductivity and a pair density wave in the kagome superconductor CsV3Sb5, and provides a basis for understanding the microscopic origin of correlated electronic states and superconductivity in vanadium-based kagome metals.

Subfields: Atomic and Molecular Physics, and Optics, Condensed Matter Physics

View Paper: https://www.semanticscholar.org/paper/d3ae4c0e55e3ac4f1b01e143f300ae0264d1ec73

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Citations in the corpus

Theory of the charge density wave in AV3Sb5 kagome metals (2021, background): “Recent experiments on kagome metals are consistent with a CDW state that doubles the unit cell in all directions (2×2×2 unit cell) and lowers the sixfold-rotational symmetry of the lattice to twofold [23, 24, 26, 31, 33].”
Electronic instabilities of kagome metals: Saddle points and Landau theory (2021, background): “5K or smaller [20, 21, 28–35], and some indications of nematicity and one-dimensional charge order in the normal and superconducting states [21, 31, 36].”
Electronic nature of chiral charge order in the kagome superconductor CsV3Sb5 (2021, background): “Consistent with previous reports [30,32,33], the tunneling spectrums show an energy gap with a gap size 2Δ=0.”