6月19日 沙特阿卜杜拉国王科技大学程斌博士学术报告：Tunable Realization of Fractional and Symmetry-Broken Chern Insulators in Bilayer-Moiré Superlattices

 

 

报告人简历：程斌，本科及硕士毕业于南京大学物理系，2015年获美国加州大学河滨分校物理系博士学位。自2016年起为沙特阿卜杜拉国王科技大学博士后研究员。 其研究方向为各类二维材料的输运和光电性质，主要包括石墨烯和二维有机-无机杂化钙钛矿。
 

摘要：Topological states of electrons have been the focus of much attention. A topological band is associated with a non-zero Chern number, which is a topological invariant of the band. With electron-electron interactions, partially filling these bands can lead to a new type of topological order called a fractional Chern insulator. These states provide a conceptually new form of topologically ordered electron systems beyond Landau levels. Hofstadter bands in a periodic moiré superlattice are ideal platforms for realizing these states as well as another class of fractional fractal states, known as symmetry-broken Chern insulators, in which the superlattice translational symmetry is broken. In our work, we study moiré superlattice systems consisting of graphene bilayers aligned to boron nitride. We demonstrate that the manifestation of symmetry-broken and fractional Chern insulators and their topology can be controlled using a perpendicular electric displacement field applied to the bilayer. Because of this tunability we observe states with new topologies that have not been previously observed.