Systematic experimental delineation of splitting, crossings, and electron-hole asymmetry in the Landau octet and higher levels of bilayer graphene

The highly tunable band structure and eightfold degeneracy of the zero-energy Landau level of bilayer graphene (BLG) make it an ideal platform for engineering new quantum Hall states. However, determining the orbital, valley and spin order of quantum Hall states at different filling factors and electric fields is still an unresolved question. In this talk, we will present systematic measurements of unprecedented precision of Landau level spectra of a BLG device at millikelvin temperatures and magnetic fields up to 14 T. The high-quality device and widely accessible electric field allow us to observe previously undetected zero-energy Landau level crossings at filling factors -2, 1 and 3 in high electric fields. In addition, we find that both zero- and high-energy Landau level crossings exhibit strong electron-hole asymmetry. Our observations enable us to constrain the parameters for constructing a realistic theoretical model, which can be used to comprehensively determine the quantum Hall states. The model also confirms states at filling factor -2 in high electric fields which had been previously unresolved. These states are both valley and orbital polarized.