Dirac electrons in topological crystalline insulators
One of the simplest but universal challenges at the frontier of materials physics is controlling band structure, both for realizing novel phenomena and for practical functionalities. In this talk, I will describe our atomic scale investigations of novel quantum materials called topological crystalline insulators (TCIs). In TCIs, topology and crystal symmetry intertwine to create massless Dirac electrons, which can be described by the same equations used for relativistic particles traveling close to the speed of light. Using Landau level spectroscopy and atomic resolution imaging in TCIs, we have discovered massive Dirac electrons coexisting with massless Dirac electrons. Our findings experimentally demonstrate the unique and extraordinary tunability of Dirac electrons in TCIs, which provides a significant step for realizing fundamentally and practically important quantum states via strain engineering. As the final part of this talk, I will also introduce our recent attempt of combing visualization techniques with epitaxial thin film based quantum materials design.