Engineering Flat Bands in InAs/GaSb Quad-layer Quantum Well Structures

Previous studies have shown that adjusting the relative thickness of InAs/GaSb double quantum wells (QWs) can transform the system from a semiconductor to a semimetal and create a dispersionless conduction band due to strong electron-hole wavefunction mixing. In our studies using k•p band structure calculations, we explore the potential to engineer flat bands in InAs/GaSb quad-layer QW materials. Using realistic band parameters and considering strain effects, our calculations show that nearly dispersionless bands can occur in specific parameter space windows. We investigate the validity of these predictions experimentally by probing the band structures of quad-layer QWs grown via molecular-beam epitaxy with magneto-infrared spectroscopy and magneto-transport. The Landau level transitions observed in this experiment can be directly compared to the optical conductivity calculated using the eight-band k•p model.