Title: Experimental observation of node-line-like surface states in LaBi,
Abstract: In a Dirac nodal line semimetal, the bulk conduction and valence bands touch
at extended lines in the Brillouin zone. To date, most of the theoretically
predicted and experimentally discovered nodal lines derive from the bulk bands
of two- and three-dimensional materials. Here, based on combined angle-resolved
photoemission spectroscopy measurements and first-principles calculations, we
report the discovery of node-line-like surface states on the (001) surface of
LaBi. These bands derive from the topological surface states of LaBi and bridge
the band gap opened by spin-orbit coupling and band inversion. Our
first-principles calculations reveal that these "nodal lines" have a tiny gap,
which is beyond typical experimental resolution. These results may provide
important information to understand the extraordinary physical properties of
LaBi, such as the extremely large magnetoresistance and resistivity plateau.