Enhanced Correlation Effects in Nodal-line Semimetal ZrSiSe

Three-dimensional (3D) Dirac fermions with highly-dispersive linear bands are usually considered weakly correlated, due to relatively large bandwidths (W) compared to Coulomb interactions (U). With the discovery of nodal-line semimetals, the Dirac dispersion has been extended to lines and loops, with reduced kinetic energy along the line [1]. However, experimental evidence for the predicted enhanced correlations in nodal-line semimetals has been rare. Here we show in ZrSiSe enhanced correlation effects through a combination of optical/magneto-optical spectroscopy and density-functional-theory (DFT) calculations. Near 40% kinetic energy reduction compared to DFT has been observed in ZrSiSe and the averaged Fermi velocity is also renormalized. ZrSiSe is therefore a novel candidate to study correlation-driven physics in Dirac systems as well as strong Berry curvature effects associated with spin-orbit-coupling.

[1] Y. Shao et al, arXiv:1806.01996 (2018)