Chaotization of internal motion of excitons in ultrathin layers by spin-orbit coupling

We show that Rashba spin-orbit coupling (SOC) can generate chaotic behavior of excitons in two-dimensional semiconductor structures. To model this chaos, we study a Kepler system with spin-orbit coupling and numerically obtain a transition to chaos at a sufficiently strong coupling. The chaos emerges since the SOC reduces the number of integrals of motion as compared to the number of degrees of freedom. Dynamically, the dependence of the exciton energy on the spin orientation in the presence of SOC produces an anomalous spin-dependent velocity resulting in chaotic motion. We observe numerically the critical dependence of the dynamics on the initial conditions, where the system can return to and exit a stability domain through very small changes in the initial spin orientation. This chaos can have a strong influence on the lifetime of optically injected carriers in semiconductors and organometallic perovskites. Hence, this effect should be taken into account while designing structures for photovoltaic and optical spintronics applications, where excitons play a significant role.