1. Department of Physics, Duke University, Durham, North Carolina 27708, United States
2. School of Mathematical Sciences, Fudan University, Shanghai 200433, China
3. Shanghai Key Laboratory for Contemporary Applied Mathematics, Shanghai 200433, China
4. Key Laboratory of Computational Physical Sciences (MOE), Shanghai 200433, China
5. Department of Mathematics, Duke University, Durham, North Carolina 27708, United States
6. Department of Chemistry, Duke University, Durham, North Carolina 27708, United States