  The double quantum well systems consisting of two HgTe layers separated by a
tunnel-transparent barrier are expected to manifest a variety of phase states
including two-dimensional gapless semimetal and two-dimensional topological
insulator. The presence of several subbands in such systems leads to a rich
filling factor diagram in the quantum Hall regime. We have performed
magnetotransport measurements of the HgTe-based double quantum wells in both
gapless and gapped state and observed numerous crossings between the Landau
levels belonging to different subbands. We analyze the Landau level crossing
patterns and compare them to the results of theoretical calculations.
