Observation of Dirac nodal line states in topological semimetal candidate PrSbTe

The interplay among topology, crystal symmetry, magnetic order, and strong electron correlation can give rise to a plethora of exotic physical phenomena. The ZrSiS family is known as typical topological Dirac semimetals, among them $\mathrm{Ln}\mathrm{SbTe}$ ($\mathrm{Ln}$ denotes lanthanide) compounds exhibit intriguing characteristics due to the presence of $\mathrm{Ln} 4f$ electrons, resulting in quantum states and unique properties. In this paper, the topological electronic structure of PrSbTe is systematically studied by angle-resolved photoemission spectroscopy (ARPES), combined with magnetic, specific heat measurements, and band structure calculations. The detailed three-dimensional electronic structure of PrSbTe has been obtained, and a diamond-shaped Fermi surface and multiple Dirac nodal lines have been observed, which are in remarkable agreement with theoretical calculations. Moreover, the $4f$ electrons in PrSbTe are rather localized, which can be revealed by on-resonant ARPES data and further confirmed by the rather small Sommerfeld coefficient of $\gamma =2.6231\mathrm{mJ}/\mathrm{mol}{K}^2$. Our results provide more detailed information about the $\mathrm{Ln}\mathrm{SbTe}$ family, which gives a deeper understanding of the interaction between $\mathrm{Ln} 4f$ electrons and the topological states.