Collapse of resonances in semiconductor heterostructures as a transition with symmetry breaking in an open quantum system

The collapse of resonances in resonant tunneling heterostructures, which is merging of two unit-transparency resonances into a single resonance with transparency less than unity has been theoretically analyzed. The electron density distribution becomes asymmetric at the collapse point in a geometrically symmetric system. The asymmetry parameter behaves as the order parameter in the second-order phase transition. The physical mechanism of the transition is associated with the broadening of the quasistationary levels of a quantum system due to the interaction with the continuum of delocalized states. The possibility of the existence of two qualitatively different types of low-energy resonances differing in the sign of the effective range of the potential has been demonstrated.