Dirac fermions with highly dispersive linear bands1,2,3 are usually considered weakly correlated due to the relatively large bandwidths (W) compared to Coulomb interactions (U). With the discovery of nodal-line semimetals, the notion of the Dirac point has been extended to lines and loops in momentum space. The anisotropy associated with nodal-line structure gives rise to greatly reduced kinetic energy along the line. However, experimental evidence for the anticipated enhanced correlations in nodal-line semimetals is sparse. Here, we report on prominent correlation effects in a nodal-line semimetal compound, ZrSiSe, through a combination of optical spectroscopy and density functional theory calculations. We observed two fundamental spectroscopic hallmarks of electronic correlations: strong reduction (1/3) of the free-carrier Drude weight and also the Fermi velocity compared to predictions of density functional band theory. The renormalization of Fermi velocity can be further controlled with an external magnetic field. ZrSiSe therefore offers the rare opportunity to investigate correlation-driven physics in a Dirac system.
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Research at Columbia on the optical properties of layered semimetals was supported as part of the Energy Frontier Research Center on Programmable Quantum Materials funded by the US Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), under award no. DE-SC0019443. Research on spin–orbit coupling in intermetallic compounds is funded by ARO grant no. W911nf-17-1-0543. D.N.B. is a Moore Foundation Investigator, EPIQS Initiative grant GBMF4533. The sample synthesis effort is supported by the US DOE under grant no. DE-SC0019068. Y.L.Z. acknowledges financial support from the National Science Foundation through the Penn State 2D Crystal Consortium-Materials Innovation Platform (2DCC-MIP) under NSF cooperative agreement DMR-1539916. J.H. acknowledges financial support from the US DOE, Office of Science, Basic Energy Sciences programme under award no. DE-SC0019467. M.I.K. acknowledges financial support from JTCFLAG-ERA project GRANSPORT. The numerical calculations presented in this paper have been partially performed at the Supercomputing Center of Wuhan University. S.M. and D.S. acknowledge support from the US DOE (DE-FG02-07ER46451) for high-field infrared measurements performed at the National High Magnetic Field Laboratory, which is supported by NSF Cooperative agreement no. DMR-1644779 and the State of Florida.
The authors declare no competing interests.
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Shao, Y., Rudenko, A.N., Hu, J. et al. Electronic correlations in nodal-line semimetals. Nat. Phys. 16, 636–641 (2020). https://doi.org/10.1038/s41567-020-0859-z
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