Anticrossing semiconducting band gap in nominally semimetallic InAs/GaSb superlattices

While (InAs)ₙ/(GaSb)ₙ (001) superlattices are semiconducting for n<nc≈28ML, for n>nc the InAs electron level eInAs is below the GaSb hole level hGaSb, so the system is converted to a nominal semimetal. At nonzero in-plane wave vectors (k_≠0), however, the wave functions eInAs and hGaSb have the same symmetry, so they anticross. This opens up a ``hybridization gap'' at some k_=k_*. Using a pseudopotential plane-wave approach as well as a (pseudopotential fit) eight-band k·p approach, we predict the hybridization gap and its properties such as wave-function localization and out-of-plane dispersion. We find that recent model calculations underestimate this gap severely.