[PAST EVENT] Physics Colloquium - Yafis Barlas

March 4, 2022
4pm - 5pm
Small Hall, Room 111
300 Ukrop Way
Williamsburg, VA 23185Map this location
Yafis Barlas

Prof. Yafis Barlas, University of Nevada - Reno, Title of talk: Topological Phases and Hofstadter butterflies in two-dimensional crystals  

Large-scale interference Moiré patterns emerge when two-dimensional (2D) crystals are rotated at relative angles, generally referred to as Twistronics. Twistronics modifies the electron’s kinetic energy, and at some “magic angles’', the kinetic energy of the electrons becomes negligible compared to their mutual electron-electron interactions. Strong interactions in flat bands result in strongly correlated and topologically ordered states owing to the interplay of topology and electron correlations. In this talk, I will discuss our recent studies of interactions and topological phases in two-dimensional crystals. First, I will discuss a new class of interacting and non-interacting symmetry-protected topological phases stabilized by mirror symmetry in ABA-stacked trilayer graphene. This quantum parity Hall state exhibits two one-dimensional counter-propagating metallic edge states, distinguished by even or odd parity under the system’s mirror reflection symmetry. Then, I will discuss electron dispersion in twisted 2D crystals at high magnetic fields, which results in fractal Hofstadter butterfly patterns in the energy spectrum. Finally. I will discuss the topological properties of Hofstadter bands as a function of twist angles and magnetic fields.