Defect scattering on the ultraclean topological semimetal PtSn4 via STM

PtSn4 is a Dirac nodal arc semimetal with high mobility and a residual resistivity ratio approaching 1000. This indicates a scarcity of scattering by defects at low temperatures. Two potential factors may be at play: PtSn4 has an extremely low defect density, and, also, some back-scattering channels may be blocked by the topological band structure.

PtSn4 has a planar structure and is easy to cleave, presenting different surface terminations suitable for a scanning tunneling microscope study. We performed topography, bias spectroscopy, and quasiparticle interference measurements (QPI) at low temperatures. Multiple defect types were found and characterized. The overall defect density is relatively low which enabled us to perform spectroscopy maps of spatially isolated defects. Most of the defects acting as scattering centers seem to reside in the Sn layers. Rarely, we observe defects with 4-fold symmetry associated with the Pt layer. Analyzing the phase information captured by the QPI allows us to identify the defects responsible for the most prominent scattering. In this talk, I will try to elucidate the origin of the extremely low residual resistance of PtSn4 as well as provide an outlook on the potential for QPI measurement to characterize band topology.