Physics (Internal)

Dirac fermions and broken symmetries in topological crystalline insulators

This event is part of the Biophysics/Condensed Matter Seminar Series.

Abstract: Topological crystalline insulators (TCIs) are a recently discovered class of topological materials which harbor massless Dirac surface states (SS). Theory predicts that these SS are protected by crystalline symmetries, and that SS electrons can acquire a mass if these symmetries are broken. In this talk, I will present our recent scanning tunneling microscopy (STM) investigations of the TCI Pb1-xSnxSe utilizing two different spectroscopic methods: quasiparticle interference imaging and Landau level spectroscopy. First, based on the interference patterns of scattered surface electrons, we uncover a distinct orbital texture of the Dirac bands in TCIs. Moreover, simultaneous imaging of the atomic and electronic structures reveals that a fraction of the Dirac electrons acquire mass due to a broken mirror symmetry. Our experiments suggest a novel pathway for manipulation of electrons in two-dimensional systems via lattice distortions.