Local, global, and nonlinear screening in twisted double-layer graphene.
One-atom-thick crystalline layers and their vertical heterostructures carry the promise of designer electronic materials that are unattainable by standard growth techniques. To realize their potential it is necessary to isolate them from environmental disturbances, in particular those introduced by the substrate. However, finding and characterizing suitable substrates, and minimizing the random potential fluctuations they introduce, has been a persistent challenge in this emerging field. Here we show that Landau-level (LL) spectroscopy offers the unique capability to quantify both the reduction of the quasiparticles' lifetime and the long-range inhomogeneity due to random potential fluctuations. Harnessing this technique together with direct scanning tunneling microscopy and numerical simulations we demonstrate that the insertion of a graphene buffer layer with a large twist angle is a very effective method to shield a 2D system from substrate interference that has the additional desirable property of preserving the electronic structure of the system under study. We further show that owing to its remarkable nonlinear screening capability a single graphene buffer layer provides better shielding than either increasing the distance to the substrate or doubling the carrier density and reduces the amplitude of the potential fluctuations in graphene to values even lower than the ones in AB-stacked bilayer graphene.
Department of Physics and Astronomy, Rutgers, The State University of New Jersey, Piscataway, NJ 08855;
Chih-Pin
CP
Lu
Department of Physics, College of William and Mary, Williamsburg, VA 23187;
Martin
M
Rodriguez-Vega
Department of Physics and Astronomy, Rutgers, The State University of New Jersey, Piscataway, NJ 08855;
Guohong
G
Li
Department of Physics and Astronomy, Rutgers, The State University of New Jersey, Piscataway, NJ 08855;
Adina
A
Luican-Mayer
Advanced Materials Laboratory, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan.
Kenji
K
Watanabe
Advanced Materials Laboratory, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan.
Takashi
T
Taniguchi
Department of Physics, College of William and Mary, Williamsburg, VA 23187;
Enrico
E
Rossi
Department of Physics and Astronomy, Rutgers, The State University of New Jersey, Piscataway, NJ 08855; eandrei@physics.rutgers.edu.
Eva Y
EY
Andrei
Landau-level spectroscopy; STM; graphene; screening