Magneto-electric Effects in Bilayer Graphene
Bilayer graphene is a carbon nanomaterial consisting of two single-layer sheets of graphite. The mobile charge carriers in this conductor turn out to be pseudospin-carrying chiral fermions having a finite band mass but zero rest energy. Our study shows that these exotic particles experience a previously unknown type of electromagnetism in which electric and magnetic fields are virtually indistinguishable: every coupling of an electron's degrees of freedom to a magnetic field is matched by an analogous coupling of the same degrees of freedom to an electric field.
This unusual duality of matter-field interactions enables novel ways to create and manipulate real-spin and layer-index-related pseudo-spin polarizations in bilayer graphene via external fields. The same mechanism also gives rise to a magneto-electric response that is normally seen in band insulators with broken inversion and time-reversal symmetries. In contrast to such systems, the magneto-electric coupling in bilayer graphene is determined by a tunable electronic degree of freedom, namely the valley isospin density, and can therefore be manipulated experimentally.