Solid State Seminar: Tunable Topological Insulators


A topological insulator is a semiconductor that has an inverted band parity. Quantum mechanical boundary conditions, the inverted band parity and symmetry arguments impose the presence of gapless Dirac states at the surface of a topological insulator. Several materials have been shown to be topological insulators among them the most studied being the Bi-based chalcogenides. Material quality challenges have so far been a major obstacle to realizing optical applications using the Bi-based materials. In this talk, I will introduce an alternative family of topological materials the Pb1-xSnxSe and Pb1-xSnxTe alloys, referred to as topological crystalline insulators (TCI). I will present experimental results that demonstrate how material quality issues are overcome in TCIs. I will then discuss magneto optical measurements that demonstrate the tunable energy gap of TCIs both for their bulk and surface states. Our results are potentially interesting for prospective optical devices covering the far- and longwave- IR spectrum.


Professor Badih Assaf
Physics Department, University of Notre Dame

Badih A. Assaf joined the Physics Department at the University of Notre Dame in August 2018 as a Freimann Assistant Professor. Prior to that, between 2014 and 2018 he held a Junior Research Chair fellowship at Ecole Normale Supérieure in Paris, France. He received his PhD from Northeastern University in 2014.


Professor Anthony Hoffman, Electrical Engineering