Multisubband plasmons in an InAs/GaSb broken-gap quantum well

Multisubband plasmon (MSP) modes in heavily doped InAs/GaSb broken-gap quantum wells grown via molecular beam epitaxy (MBE) are investigated. An eight-band <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:mrow> <a:mover accent="true"> <a:mi>k</a:mi> <a:mo>⃗</a:mo> </a:mover> <a:mo>·</a:mo> <a:mover accent="true"> <a:mi>p</a:mi> <a:mo>⃗</a:mo> </a:mover> </a:mrow> </a:math> semiclassical model accurately predicts ellipsometric spectra, reflecting strong subband hybridization and nonparabolicity. In contrast, single-band plasmon models show qualitative discrepancies with experiment, even with adjusted effective masses. These findings highlight the potential of broken-gap wells for quantum technologies leveraging interband coupling and wavefunction hybridization.