Transport Gap in Suspended Bilayer Graphene at Zero Magnetic Field

• Published in: arXiv.org
• Main Authors: Veligura, A, van Elferen, H J, Tombros, N, Maan, J C, Zeitler, U, van Wees, B J
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 28.03.2012
• Subjects: Antiferromagnetism; Bilayers; Broken symmetry; Carrier density; Dependence; Graphene; Magnetic fields; Physics - Mesoscale and Nanoscale Physics; Splitting
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1202.1753

We report a change of three orders of magnitudes in the resistance of a suspended bilayer graphene flake which varies from a few k\(\Omega\)s in the high carrier density regime to several M\(\Omega\)s around the charge neutrality point (CNP). The corresponding transport gap is 8 meV at 0.3 K. The sequence of appearing quantum Hall plateaus at filling factor \(\nu=2\) followed by \(\nu=1\) suggests that the observed gap is caused by the symmetry breaking of the lowest Landau level. Investigation of the gap in a tilted magnetic field indicates that the resistance at the CNP shows a weak linear decrease for increasing total magnetic field. Those observations are in agreement with a spontaneous valley splitting at zero magnetic field followed by splitting of the spins originating from different valleys with increasing magnetic field. Both, the transport gap and \(B\) field response point toward spin polarized layer antiferromagnetic state as a ground state in the bilayer graphene sample. The observed non-trivial dependence of the gap value on the normal component of \(B\) suggests possible exchange mechanisms in the system.