Dirac nodal line and Rashba spin-split surface states in nonsymmorphic ZrGeTe

Dirac semimetals (DSMs) are three-dimensional analogue to graphene with symmetry enforced bulk Dirac nodes. Among various DSMs, ZrSiS has attracted great interests recently, due to its three dimensional Dirac nodal line protected by the nonsymmorphic symmetry. It belongs to a large family of isostructural compounds with rich quantum phenomenon. Here we present a comprehensive study of the first principle calculation, angle-resolved photoemission spectroscopy measurements, and scanning tunneling microscope experiments on ZrGeTe, a member of the ZrSiS family with stronger spin-orbit coupling (SOC). Our band structure calculation shows Dirac line nodes along (AM) over bar and (XR) over bar, the signature of linearly dispersive diamond-shaped band around (Gamma) over bar , and the existence of floating gapless surface states at (X) over bar with Rashba spin-split helical spin texture. Furthermore, characteristic q-vectors including two Umklapp scattering vectors revealed by our quasiparticle scattering interference imaging can be identified with joint density of states simulation based on our calculated band structure. Our results demonstrate the effects of large SOC on the electronic structure of ZrGeTe, which may benefit the potential application by utilizing its exotic quantum states in the future.