Superlattice-Induced Insulating States and Valley-Protected Orbits in Twisted Bilayer Graphene.
Twisted bilayer graphene (TBLG) is one of the simplest van der Waals heterostructures, yet it yields a complex electronic system with intricate interplay between moiré physics and interlayer hybridization effects. We report on electronic transport measurements of high mobility small angle TBLG devices showing clear evidence for insulating states at the superlattice band edges, with thermal activation gaps several times larger than theoretically predicted. Moreover, Shubnikov-de Haas oscillations and tight binding calculations reveal that the band structure consists of two intersecting Fermi contours whose crossing points are effectively unhybridized. We attribute this to exponentially suppressed interlayer hopping amplitudes for momentum transfers larger than the moiré wave vector.
Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Y
Y
Cao
Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
J Y
JY
Luo
Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
V
V
Fatemi
Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.
S
S
Fang
Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.
J D
JD
Sanchez-Yamagishi
National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan.
K
K
Watanabe
National Institute for Materials Science, Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan.
T
T
Taniguchi
Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.|John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA.
E
E
Kaxiras
Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
P
P
Jarillo-Herrero