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SUMMARY:Exciton Superfluid and Ferromagnetic Superconductivity in Graphene
  - Prof Philip Kim\, Harvard University 
DTSTART:20190531T133000Z
DTEND:20190531T143000Z
UID:TALK125392@talks.cam.ac.uk
CONTACT:Olivia Matthewson
DESCRIPTION:Superfluid and superconductors are two prototypical examples o
 f quantum condensates of bosonic particles. By controlling the interaction
  between two fermionic particles\, a composite boson can be formed by pair
 ing fermions. A crossover behavior from weak coupling superconducting Bard
 een-Cooper-Schrieffer (BCS) pairing to a superfluid Bose-Einstein condensa
 te (BEC) of tightly bound pairs has been expected as a function of the att
 ractive interaction in Fermi systems. In this talk\, we will discuss two s
 uch examples realized in graphene heterostructures. In the first part of t
 he presentation\, we will discuss an experimental demonstration of magneto
 exciton condensation. Employing two layers of graphene separated by an ato
 mically thin insulator\, we realize a superfluid condensation of magnetic-
 field-induced excitons across the double layers of graphene probed by Coul
 omb drag. Here\, we observe dissipationless exciton motion in this system 
 across the BEC-BCS phase boundary controlled by the magnetic field. In the
  second part of the presentation\, we will discuss the recent development 
 of unconventional superconductivity appeared in twisted double graphene bi
 layers with small twisting angles. We observed that a ferromagnetic correl
 ated insulating state appears by controlling the flatness of the bilayer g
 raphene band using the perpendicular electric field applied by the gate. U
 pon doping this ferromagnetic insulator\, we obtain the superconductivity\
 , whose transition temperature can be controlled by electric fields. Remar
 kably\, we find that increasing in-plane magnetic field increases supercon
 ducting transition temperature\, suggesting unconventional superconductivi
 ty with spin-polarized cooper pairs.
LOCATION: Small Lecture Theatre\, Cavendish Laboratory\, J.J. Thomson Aven
 ue
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