CPM Seminar

Topological phases in graphene

Zlatko Papic

Perimeter Institute/Waterloo Institute for Quantum Computing

As realized for the first time in 1980s, quantum systems in reduced spatial dimensions can sometimes undergo a special type of ordering which does not break any symmetry but introduces long-range entanglement and emergent excitations that have radically different properties from their original constituents. Most of our experimental knowledge of such “topological” phases of matter comes from studies of two-dimensional electron gases in GaAs semiconductors in high magnetic fields and at low temperatures. In the first part of this talk, I will give an introduction to these systems and review some latest theoretical developments related to the physics of the non-Abelian states and the interplay of symmetry breaking with quantum geometry. In the second part, I will discuss new directions for experimental realization and study of the topological phases, focusing in particular on bilayer graphene. I will present evidence that this material supports the “even-denominator” fractional state, whose observation has recently been reported, which is related to the Moore-Read state. Finally, I will outline several proposals for the tunability of the effective electron-electron interactions in graphene systems, which might enable further experimental progress beyond GaAs.