Accurate determination of electron-hole asymmetry and next-nearest neighbor hopping in graphene
Physical Review B
American Physical Society
The next-nearest neighbor hopping term t' determines a magnitude and, hence, importance of several phenomena in graphene, which include self-doping due to broken bonds and the Klein tunneling that in the presence of t' is no longer perfect. Theoretical estimates for t' vary widely whereas a few existing measurements by using polarization resolved magneto-spectroscopy have found surprisingly large t', close or even exceeding highest theoretical values. Here we report dedicated measurements of the density of states in graphene by using high-quality capacitance devices. The density of states exhibits a pronounced electron-hole asymmetry that increases linearly with energy. This behavior yields t' approx -0.30 eV +-15%, in agreement with the high end of theory estimates. We discuss the role of electron-electron interactions in determining t' and overview phenomena which can be influenced by such a large value of t'.
We acknowledge financial support from the European Research Council, the Royal Society, the Spanish Ministry of Economy (MINECO) through Grant No. FIS2011-23713, the European Research Council Advanced Grant (Contract No. 290846), and from European Commission under the Graphene Flagship (Contract No. CNECT-ICT-604391.
This is the author accepted manuscript. The final version is available from the American Physical Society via the DOI in this record.
Vol. 88, article 165427