| AVS 64th International Symposium & Exhibition | |
| 2D Materials Focus Topic | Thursday Sessions |
| Session 2D+MI-ThM |
| Session: | Novel Quantum Phenomena in 2D Materials |
| Presenter: | Daniel Walkup, NIST/CNST |
| Authors: | D. Walkup, NIST/CNST F. Ghahari, NIST/CNST C. Gutierrez, NIST/CNST J.F. Rodriquez-Nieva, Harvard University Y. Zhao, NIST/CNST J. Wyrick, NIST/CNST F.D. Natterer, NIST/CNST W.G. Cullen, NIST/CNST K. Watanabe, National Institute for Materials Science, Japan T. Tanaguchi, National Institute for Materials Science, Japan L.S. Levitov, MIT N.B. Zhitenev, NIST/CNST J.A. Stroscio, NIST/CNST |
| Correspondent: | Click to Email |
In graphene and other 2D Dirac materials, the band structure has the property that momentum-space paths enclosing the Dirac point pick up a Berry phase of π. In a uniform magnetic field, this leads to a special quantization rule and an N=0 Landau level at the Dirac point. In a circular graphene resonator, weak magnetic fields can tune the quantized electron orbits between states with Berry phases of zero and π, leading to a discontinuous jump in the quantum energy level as a function of applied field. Here we report scanning tunneling microscopy and spectroscopy (STM/S) studies of circular resonators fabricated in p-n junction rings in graphene/hBN backgated devices. We observe direct signatures of a Berry-phase-induced switching of the resonator states measured with scanning tunneling spectroscopy as a function of magnetic field. The telltale signature is a sudden and large increase in the energy of angular-momentum states in the graphene p-n junction resonators when a small critical magnetic field is reached, in agreement with theoretical calculations of Dirac potential wells.