A Type-II Dirac Semimetal*

Topological materials have been a widely researched topic in condensed matter physics due to their unique quantum properties observable at a macroscopic scale, protected by certain intrinsic symmetries. Here, we study a transition metal dichalcogenide (TMD) platinum ditelluride (or PtTe₂), which is classified as a Type II Dirac Semimetal. Type II Dirac Semimetals are characterized by the presence of Dirac points formed by a fourfold overlap of two doubly degenerate energy bands in momentum space, where both time reversal and inversion symmetry are present. Excitations at these band crossing are not constrained by Lorentz invariance, which leads to highly tilted Dirac cones. Here, we use scanning tunneling microscopy to investigate PtTe₂, which serves as a baseline for understanding the electronic structure of random Chromium alloys of the same material that introduce magnetic ordering. Current data gathered from preliminary measurements exhibit atomically flat terraces, separated by step sizes consistent with the expected atomic structure. Point defects on the surface were also seen in higher resolution images, though atomic resolution of the PtTe₂ lattice require further sample preparation. Measurements were made at 100K on bulk PtTe₂ crystals, which were mechanically exfoliated in UHV to produce clean surfaces.