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Non-trivial band topology and orbital-selective electronic nematicity in a titanium-based kagome superconductor

Abstract

Electronic nematicity that spontaneously breaks rotational symmetry is a generic phenomenon in correlated quantum systems including high-temperature superconductors and the AV3Sb5 (A can be K, Rb or Cs) family of kagome superconductors. However, the underlying mechanism of nematicity in these systems is hard to identify because of its entanglement with other ordered phases. Recently, a family of titanium-based kagome superconductors ATi3Bi5 have been synthesized, where electronic nematicity occurs in the absence of charge order. It provides a platform to study nematicity in its pure form, as well as its interplay with orbital degrees of freedom. Here we reveal the band topology and orbital characters of the multiorbital RbTi3Bi5. We use polarization-dependent angle-resolved photoemission spectroscopy with density functional theory to identify the coexistence of flat bands, type-II Dirac nodal lines and non-trivial topology in this compound. Our study demonstrates the change in orbital character along the Fermi surface contributed by the kagome bands, implying a strong intrinsic interorbital coupling in the Ti-based kagome metals. Furthermore, doping-dependent measurements uncover the orbital-selective features in the kagome bands, which can be explained by dp hybridization. Hence, interorbital coupling together with dp hybridization is probably the origin of electronic nematicity in ATi3Bi5.

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Fig. 1: Crystal structure and calculated band structure of RbTi3Bi5.
Fig. 2: Polarization-dependent measurements of the kagome bands.
Fig. 3: 2 topological surface states in RbTi3Bi5.
Fig. 4: Orbital-selective doping effect and dp hybridization in RbTi3Bi5.

Data availability

All data needed to evaluate the conclusions in the paper are present in the paper and/or the Supplementary Information. All other data that support the findings of this study are available from the corresponding authors upon reasonable request. Source data are provided with this paper.

Code availability

The band structures used in this study are available from the corresponding authors upon reasonable request.

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Acknowledgements

Work at the Paul Scherrer Institut was supported by the Swiss National Science Foundation under grant no. 200021_188413. X.W. was supported by the National Natural Science Foundation of China (grant no. 12047503). J.M. was supported by the Research Grants Council of Hong Kong via Early Career Scheme (21304023), the Collaborative Research Fund (C6033-22G), the Collaborative Research Equipment Grant (C1018-22E) and the National Natural Science Foundation of China (12104379). J.H. was supported by the Ministry of Science and Technology (grant no. 2022YFA1403901), the National Natural Science Foundation of China (grant no. NSFC-11888101) and the New Cornerstone Foundation.

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Authors

Contributions

Y.H. and M.S. conceived the ARPES experiments. Z.Z. grew and characterized the crystals with guidance from H.C., H.Y. and H.-J.G. X.W. and C.L. performed the theoretical calculations and analysis with support from A.P.S. and J.H. Y.H. performed the ARPES experiments with help from J.M., M.R. and M.S. Y.Z. and J.L. performed the transport measurements with guidance from X.D. N.C.P. maintained the ARPES facilities at ULTRA, SIS. Y.H. analysed the data. Y.H. and X.W. wrote the paper with inputs from all authors.

Corresponding authors

Correspondence to Yong Hu, Xianxin Wu, Hong-Jun Gao or Ming Shi.

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Supplementary information

Supplementary Information

Supplementary Sections 1–8 and Figs. 1–8.

Source data

Source Data Fig. 1

Magnetic susceptibilities, temperature-dependent resistivity and DFT-calculated band dispersions of RbTi3Bi5.

Source Data Fig. 2

DFT-calculated electronic structure and ARPES spectra for the flat bands.

Source Data Fig. 4

Doping-dependent EDCs and orbital-resolved DFT-calculated band dispersion.

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Hu, Y., Le, C., Zhang, Y. et al. Non-trivial band topology and orbital-selective electronic nematicity in a titanium-based kagome superconductor. Nat. Phys. 19, 1827–1833 (2023). https://doi.org/10.1038/s41567-023-02215-z

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