Quantum mechanics of 2D electron crystals

The low-carrier density state of a 2D semiconductor is described in terms of the homogeneous two-dimensional electron gas (2DEG), the ground state properties of which are determined by the electron density. Below a critical density, the electronic system freezes into a triangular lattice electron solid, or Wigner crystal. For experimentally relevant carrier concentrations the electron solid is highly quantum-mechanical, the significant overlap between localized electronic orbitals leading to frequent electron tunneling between Wigner crystal lattice sites. I will describe some new theoretical results exploring the consequences of these quantum effects in monolayer and bilayer 2DEGs: In the monolayer case, increasing electron density may drive the Wigner crystal into a metallic charge-density wave state that can be understood as quantum crystal with a finite concentration of itinerant ground-state defects, while in the bilayer case interlayer Coulomb interactions lead to new lattice geometries in which ring-exchange processes lead to a variety of interesting magnetic ground states.

Speaker: Ilya Esterlis, University of Wisconsin - Madison