L. Fu Colloquium: Electrons in Pairs and Fractions: New Phases in 2D Quantum Materials

Electrons in solids can pair up to form superconductors—or even break apart into fractionally charged particles. These remarkable behaviors were once thought to be mutually exclusive, requiring opposite physical conditions. In this talk, I will show how superconductivity, fractionalization, and ferromagnetism can all emerge in two-dimensional materials with flat topological bands, and how these phases can transform into one another. In particular, the superconducting state features electron pairs with finite orbital angular momentum and zero-energy Majorana fermions, realizing a chiral topological superconductor—a new phase of matter.