Fragility of Fermi arcs in Dirac semimetals

Abstract

We use tunable, vacuum ultraviolet laser based angle-resolved photoemission spectroscopy and density functional theory (DFT) calculations to study the electronic properties of Dirac semimetal candidate cubic ${\mathrm{PtBi}}_{2}$. In addition to bulk electronic states we also find surface states in ${\mathrm{PtBi}}_{2}$, which is expected as ${\mathrm{PtBi}}_{2}$ was theoretically predicated to be a candidate Dirac semimetal. The surface states are also well reproduced from DFT band calculations. Interestingly, the topological surface states form Fermi contours rather than double Fermi arcs that were observed in ${\mathrm{Na}}_{3}\mathrm{Bi}$. The surface bands forming the Fermi contours merge with bulk bands in proximity to the Dirac point projections, as expected. Our data confirm the existence of Dirac states in ${\mathrm{PtBi}}_{2}$ and reveal the fragility of the Fermi arcs in Dirac semimetals. Because the Fermi arcs are not topologically protected in general, they can be deformed into Fermi contours, as proposed by M. Kargarian et al. [Proc. Natl. Acad. Sci. USA 113, 8648 (2016)]. Our results demonstrate the validity of this theory in ${\mathrm{PtBi}}_{2}$.