Past Events

Abstract:

Bilayer graphene comprises two coupled single-layer graphene sheets. Its properties can be considered to be intermediate between the single-layer graphene case and a regular semiconductor --- the quasiparticles of bilayer graphene are massive and have a gapless parabolic dispersion (similar to a regular semiconductor), and yet carry a momentum-dependent pseudospin (similar to single-layer graphene). One of the most interesting physics in bilayer graphene is the interband optical conductivity, which exhibits a universal value of e² /2ħ, related to its momentum-space Berry phase 2π. In this talk, I will discuss many-body effects on the optical conductivity of doped bilayer graphene arising from electron-electron Coulomb interaction. In contrast to usual metals and semiconductors whose effective Hamiltonians are Galilean invariant, the chiral structure of bilayer graphene explicitly breaks Galilean invariance, and consequently electron-electron interaction will renormalize their transport properties. I will also discuss a new coupling mechanism between the intraband (i.e., Drude) and interband channels of the optical conductivity, which gives rise to an interaction-induced renormalization of the long-wavelength plasmon frequency.

Coffee and tea will be served 20 minutes prior to the seminar.