Robust non-Abelian phases and continuous quantum phase transitions in a half-filled bilayer graphene Landau level

Event Dates: 

Thursday, November 10, 2016 - 12:00pm

CTQM Seminar Type: 

  • Related Seminar Series

Speaker Name(s): 

Michael Zaletel

Speaker Affiliation(s): 

Princeton University

Abstract, Event Details: 

Bilayer graphene in a large magnetic field displays a rich interplay of fractionalized quantum Hall states and symmetry breaking due to its spin, valley, and orbital degeneracies. The splitting of these degeneracies can be controlled in situ with electric and magnetic fields, revealing a plethora of quantum phase transitions at fixed filling fraction. I will discuss recent experiments which reveal for the first time a robust even-denominator fractional quantum Hall state in a fully controllable bilayer graphene device. Numerical calculations suggest this state is in the non-Abelian “Pfaffian” phase. A perpendicular electric field is observed to cause a transition from this Pfaffian state into a composite Fermi liquid, and I will explain a scenario in which the transition is mediated by novel inter-valley excitons which form an “exciton Fermi sea.”