Nonsymmorphic symmetry-protected band crossings in a square-net metal PtPb4
Han Wu, Alannah M. Hallas, Xiaochan Cai, Jianwei Huang, Ji Seop Oh, Vaideesh Loganathan, Ashley Weiland, Gregory T. McCandless, Julia Y. Chan, Sung‐Kwan Mo, Dong-Hui Lu, Makoto Hashimoto, Jonathan D. Denlinger, R. J. Birgeneau, Andriy H. Nevidomskyy, Gang Li, E. Morosan, Ming Yi
Abstract
Abstract Topological semimetals with symmetry-protected band crossings have emerged as a rich landscape to explore intriguing electronic phenomena. Nonsymmorphic symmetries in particular have been shown to play an important role in protecting the crossings along a line (rather than a point) in momentum space. Here we report experimental and theoretical evidence for Dirac nodal line crossings along the Brillouin zone boundaries in PtPb 4 , arising from the nonsymmorphic symmetry of its crystal structure. Interestingly, while the nodal lines would remain gapless in the absence of spin–orbit coupling (SOC), the SOC, in this case, plays a detrimental role to topology by lifting the band degeneracy everywhere except at a set of isolated points. Nevertheless, the nodal line is observed to have a bandwidth much smaller than that found in density functional theory (DFT). Our findings reveal PtPb 4 to be a material system with narrow crossings approximately protected by nonsymmorphic crystalline symmetries.