“…The study of multiband models is a very active area of research (Ben Abdallah and Kefi, 2008;Barletti and Frosai, 2010;Barletti, Frosali, and Demeio, 2007;Barletto and Mahats, 2010;Mahats, 2005;Ben Abdallah, Jourdana, and Pietra, 2012;Pinaud, 2004;Barletti and Ben Abdallah, 2011;Morandi and Schuerrer, 2011;Morandi, Hervieux, and Manfredi, 2010;Morandi and Demeio, 2008). A considerable effort has been made in order to develop mathematical models that reproduce the steady states and the out-of-equilibrium dynamics in heterostructure devices (Ben Abdallah and Mehats 2004).…”