Electronic Density of States in Nonsymmorphic PdSb$$_2$$

Abstract PdSb $$_2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mn>2</mml:mn> <mml:mrow/> </mml:mmultiscripts> </mml:math> is a metal in which band structure calculations suggest the presence of sixfold-degenerate fermions. Surface bands emerging from the sixfold-degenerate point may exhibit nontrivial topological properties. Here, we present Scanning Tunneling Microscopy (STM) measurements of PdSb $$_2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mn>2</mml:mn> <mml:mrow/> </mml:mmultiscripts> </mml:math> between 4.2 and 60 K and under magnetic fields up to 14 T. We identify a gap-like feature with a width of approximately 20 meV around the Fermi level. We additionally provide Density Functional Theory (DFT) calculations and discuss the possible connection between the observed tunneling conductance and the surface band structure. We find a small incomplete gap-like feature in the density of states which has a similar size as the feature observed in the experiment but is located slightly above the Fermi level. We furthermore estimate surface relaxation of atomic positions and find that Sb suffers larger relaxations than Pd atoms. This could influence the position in energy of the features found in the band structure. Our measurements show that PdSb $$_2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mn>2</mml:mn> <mml:mrow/> </mml:mmultiscripts> </mml:math> is a good metal, with a density of states which presents, however, interesting features close to the Fermi level.