| AVS 58th Annual International Symposium and Exhibition | |
| Graphene and Related Materials Focus Topic | Tuesday Sessions |
| Session GR+MI-TuA |
| Session: | Graphene: Magnetic Properties and Spin-Dependent Phenomena |
| Presenter: | Suyong Jung, NIST |
| Authors: | S. Jung, NIST N.N. Klimov, NIST D.B. Newell, NIST N.B. Zhitenev, NIST J.A. Stroscio, NIST |
| Correspondent: | Click to Email |
We have performed scanning tunneling spectroscopy measurements on a gated bilayer graphene device. In graphene bilayer, a potential asymmetry between the layers induces an energy gap in the electron spectrum. The formation of the energy gap is investigated as a function of carrier density and magnetic field. We found that in zero magnetic field, the reliable determination of the gap can be complicated because of disorder scattering. However, in the quantum Hall regime, the energy gap can be quantitatively determined by measuring the layer-polarized low index Landau levels.
Our scanning tunneling spectroscopy measurements reveal that the microscopic nature of the bilayer gap is very different from what was observed in previous macroscopic measurements or expected from current theoretical models. The potential asymmetry varies spatially in both magnitude and sign on a nanometer length scale, showing strong correlation with the disorder potential. This random pattern of alternating dipole fields is qualitatively consistent with the reduced disorder-induced density fluctuations in the top layer.