Defect scattering in the Ultraclean Dirac nodal arc semimetal PtSn₄

PtSn4 was reported to be a Dirac nodal arc semimetal with a high residual resistivity ratio as high as 3000 and extremely large magnetoresistance (XMR). While the former feature is indicative of a scarcity of scattering by defects at low temperatures, the XMR has been attributed to the compensation of electron and hole charge carriers on its Fermi surface.

Using Scanning Tunnelling Microscopy (STM) and Spectroscopy (STS) and Quasiparticle Interference (QPI), we investigated the topography, electronic structure, and scattering by defects at low temperatures. The low defect density enables spectroscopic maps and QPI measurements of spatially isolated defects. Most defects appear to reside in the Sn layers. Rarely, we observe defects with 4-fold symmetric appearance associated with the Pt layer. The defect densities expected from starting impurities and RRR are compared with the observed densities, while information captured by the QPI allows us to identify the defects responsible for the most prominent scattering.

Aided by ab-initio calculations, we compare the scattering features observed in QPI to the band structure and study the composition and topology of the Fermi surface.