Lifting of the Landau level degeneracy in graphene devices in a tilted magnetic field

摘要

We report on transport and capacitance measurements of graphene devices inmagnetic fields up to 30 T. In both techniques, we observe the full splittingof Landau levels and we employ tilted field experiments to address the originof the observed broken symmetry states. In the lowest energy level, the spindegeneracy is removed at filling factors $\nu=\pm1$ and we observe an enhancedenergy gap. In the higher levels, the valley degeneracy is removed at oddfilling factors while spin polarized states are formed at even $\nu$. Althoughthe observation of odd filling factors in the higher levels points towards thespontaneous origin of the splitting, we find that the main contribution to thegap at $\nu= -4,-8$, and $-12$ is due to the Zeeman energy.