Exciton wave function localization and exciton diamagnetic coefficient in semiconductor quantum rings without reflection symmetry

Abstract

We theoretically study how reflection asymmetry affects the neutral exciton diamagnetic coefficient in self-assembled InGaAs/GaAs semiconductor wobbled quantum rings. The previously proposed mapping method is used to simulate the exciton wave function and energy in the rings. The description is suited to clarify the important question of the exciton diamagnetic coefficient stability in the rings with broken reflection symmetry. Our simulation results confirm that the exciton wave function of the reflection symmetrical (balanced) wobbled ring is distributed equally over two potential valleys corresponding to the hills in the ring's shape. At the same time, even a very small reflectional imbalance in the geometry and (or) material content of the wobbled rings destroys the ringlike shape of the exciton wave function and causes the localization of the function in one of the potential valleys of the ring (dotlike shape of the exciton wave function). This leads to a rapid decrease of the exciton diamagnetic coefficient. Our calculation results are in good agreement with recent experimental observations.