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**Special Colloquium** Dirac fermions and broken symmetries in topological crystalline insulators

Event Details

Event Dates: 

Thursday, February 5, 2015 - 4:00pm

Seminar Location: 

  • Duane Physics Room G1B30

Speaker Name(s): 

Ilijia Zeljkovic

Speaker Affiliation(s): 

Madhavan Lab, Boston College
Seminar Type/Subject

Scientific Seminar Type: 

  • Physics Department Colloquium

Event Details & 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.