[qmeso-seminar] семинар сектора 20 сентября

[Mikhail A. Skvortsov]

                     СЕМИНАР СЕКТОРА КВАНТОВОЙ МЕЗОСКОПИКИ

                        пятница 20 сентября, 15:00, ИТФ


                                М. Сербин (MIT)

New Dirac points and multiple Landau level crossings in biased trilayer graphene


Recently a new high-mobility Dirac material, trilayer graphene, was realized
experimentally. The band structure of ABA-stacked trilayer graphene consists of
a monolayer-like and a bilayer-like pair of bands. Here we study electronic
properties of ABA-stacked trilayer graphene biased by a perpendicular electric
field. We find that the combination of the bias and trigonal warping gives rise
to a set of new Dirac points: In each valley, seven species of Dirac fermions
with small masses of order of a few meV emerge. The positions and masses of the
emergent Dirac fermions are tunable by bias, and one group of Dirac fermions
becomes massless at a certain bias value.

Further, we analyze the evolution of the Landau level spectrum as a function of
bias. We develop a theoretical model and argue that, in contrast to monolayer
and bilayer graphene, the Landau level splittings and quantum Hall phase
transitions observed in a recent experiment can be understood within a
single-particle picture, but imply the presence of a charge density imbalance
between the inner and outer layers of TLG, even at charge neutrality and zero
transverse electric field. Our results indicate the importance of a previously
unaccounted band structure parameter. We show that the pattern of Landau level
crossings is very sensitive to certain band structure parameters, and can
therefore provide a useful tool for determining their precise values.