SPA Colloquium: Tomohiro Soejima (Harvard University)

Title: Trapping topological electrons in two-dimensional materials

Abstract: Wave-particle duality is one of the most fundamental features of quantum mechanics. Two solid state systems, this duality clearly manifests itself as different phases of matter: metals, which reflect the wave nature of electrons, while so-called Wigner crystals reflect the particle, and therefore classical, nature of electrons in the presence of strong interactions.

However, these are not all quantum mechanics has to offer in solid state systems. They can also give rise to topological nontrivial effects, which, remarkably, can be diagnosed by measuring their Hall conductance.
In this talk, I will introduce anomalous Hall crystals (AHC), which marry the seemingly classical behavior of Wigner crystals with nontrivial topology. These crystals may arise in highly engineered two-dimensional materials, where quantum effects are enhanced by a strong coupling between momentum and pseudospin that results in large Berry curvature. I will discuss when these crystals are stabilized in various model Hamiltonians, and how their nontrivial topology may or may not affect their dynamical properties such as center of mass motion. Finally, I will talk about the possibility of engineering so-called fractional phases out of AHCs.