Physics Colloquium: Topological semimetals and their quantum responses
Guoqing Chang, Princeton University
Abstract: Finding new phases of matter and understanding their physics are primary goals of condensed matter physics. Topological states are new phases of matter characterized by quantized topological invariants. Topological quantum materials can support protected boundary states, realize elusive quasi-particles, and exhibit novel electronic, magnetic, and optical responses. Theoretical and experimental advances in topological quantum materials can breed novel technologies. A new frontier in the field of quantum materials is topological semimetals.
First, I will discuss how crystalline symmetries can protect novel quantum semi-metallic phases. In particular, I will focus on topological quantum properties of structurally chiral crystals and topological Hopf-link protected by mirror symmetries. Both our theoretical predictions and experimental observations will be presented. Second, I will present the magnetic-field and nonlinear optical responses of topological semimetals, which probe the local Berry curvature in energy-momentum space. I will highlight our prediction of quantized photogalvanic effects in the chiral crystal RhSi family and the latest experimental evidence of the exotic quantum phenomenon. Finally, I will show how current works suggest ample exciting possibilities to discover new fundamental quantum physics, which could pave the way for the next-generation quantum technologies.
Tuesday, February 18 at 3:15pm
Regents Hall, 109
3700 O St. NW