THz magnetospectroscopy of double HgTe quantum well

We report on the first THz magnetospectroscopy of double HgTe quantum well in magnetic fields up to 16 T. Very recently, specific metal phase, which holds some properties of natural bilayer graphene, was predicted in this system. In this work, we focus on the double HgTe QW with parameters, corresponding to such `bilayer graphene' phase. In our experiments we clearly observe THz optical transitions from double-degenerated zero-mode Landau level. A good agreement between experimental and theoretical transition energies confirms previous prediction of `bilayer graphene' phase in double HgTe quantum wells.