Observation of gapless nodal-line states in NdSbTe
Sabin Regmi, Robert L. Smith, Anup Pradhan Sakhya, Milo Sprague, Mazharul Islam Mondal, Iftakhar Bin Elius, Nathan Valadez, Andrzej Ptok, D. Kaczorowski, Madhab Neupane
Abstract
Lanthanide ($Ln$)-based systems in $\mathrm{ZrSiS}$-type nodal-line semimetals have been subjects of research investigations as grounds for studying the interplay of topology with possible magnetic ordering and electronic correlations that may originate from the presence of $Ln\phantom{\rule{0.28em}{0ex}}4f$ electrons. In this study, we carried out a thorough study of a $Ln\mathrm{SbTe}$ system, $\mathrm{NdSbTe}$, by using angle-resolved photoemission spectroscopy along with first-principles calculations and thermodynamic measurements. We experimentally detect the presence of multiple gapless nodal-line states, which is well supported by first-principles calculations. A dispersive and an almost nondispersive nodal line exist along the bulk $X\text{\ensuremath{-}}R$ direction. Another nodal line is present well below the Fermi level across the $\mathrm{\ensuremath{\Gamma}}\text{\ensuremath{-}}M$ direction, which is formed by bands with high Fermi velocity that seem to be sensitive to light polarization. Our study provides insight into the electronic structure of an alternative $Ln\mathrm{SbTe}$ material system that will aid towards understanding the connection of $Ln$ elements with topological electronic structures in these systems.