Abstract
Helical conductors with spin-momentum locking are promising platforms for Majorana fermions. Here we report observation of two topologically distinct phases supporting helical edge states in charge neutral Bernal-stacked tetralayer graphene in Hall bar and Corbino geometries. As the magnetic field and out-of-plane displacement field are varied, we observe a phase diagram consisting of an insulating phase and two metallic phases, with 0, 1, and 2 helical edge states, respectively. These phases are accounted for by a theoretical model that relates their conductance to spin-polarization plateaus. Transitions between them arise from a competition among interlayer hopping, electrostatic and exchange interaction energies. Our work highlights the complex competing symmetries and the rich quantum phases in few-layer graphene.
- Received 3 December 2019
- Accepted 15 June 2020
- Corrected 18 November 2020
DOI:https://doi.org/10.1103/PhysRevLett.125.036803
© 2020 American Physical Society
Physics Subject Headings (PhySH)
Corrections
18 November 2020
Correction: A missing statement of support has been added to the Acknowledgments section.