When two-dimensional materials are placed in a strong perpendicular magnetic field, the energy levels of the electrons are quantized into the so-called Landau levels (LL). Optical transitions between these discrete energy levels can often reveal crucial information regarding the electronic properties of the parent material, such as the band structure and electron correlations. The usual optical transitions in pristine bilayer graphene have been well understood and summarized in a set of selection rules that are associated with the LL index. In this work, the authors perform photocurrent spectroscopy measurements on high-quality bilayer graphene samples and study the optical transitions between different Landau levels. For the first time, they observed optical transitions that go beyond the usual transition rules, which can be attributed to the presence of strong electron correlations.
Read more at Nature Communications:
https://doi.org/10.1038/s41467-020-16844-y
10 Jun 2020