Nonsymmorphic Symmetry-Protected Band Crossings in a Correlated Metal

Topological semimetals in which the bulk bands cross at points without opening an energy gap have emerged as a particularly rich platform to explore novel electronic phenomena. In nodal line semimetals, the bulk band linear crossings extend from discrete points to continuous lines or loops in momentum space. Crystalline symmetries, such as nonsymmorphic symmetry, can play a crucial role in protecting the band crossings along a continuous line or loop in momentum space in TSM. Nonsymmorphic symmetry will generate a band folding with crossings at the Brillouin zone (BZ) boundaries that are protected against spin orbital coupling. Here we will present our recent combined theory and angle-resolved photoemission spectroscopy study on PtPb₄. We will show the existence of nonsymmorphic symmetry protected Dirac nodal lines in this material system as well as demonstrate the effect of moderate electron correlations on the measured band structure_.