Competing mechanisms and temperature effects within the static nonlinear optical response 

The nonlinear optical response of a material is a powerful technological tool used in various applications from characterization of materials to photovoltaics. Within the static regime, the shift current has been studied extensively. Two other responses however, namely the injection current and optical rectification¹, has remained largely neglected. We present a systematic investigation of all three phenomena using a general framework for the static nonlinear response with the inclusion of many-body electron-hole interactions and present ab-initio calculations using the state-of-the-art GW-BSE method. Our calculations show that the generation of these three responses are not mutually exclusive, instead they each contribute to the current generation through a different mechanism.  We further investigate the relationship between these mechanisms and their temperature dependence by considering exciton-phonon interactions and show theoretically the existence of a below-gap response of optical rectification made possible due to these interactions. Our work provides a guide on the designing principles for nonlinear optical devices.  

 

1. Sipe, J. E., & Shkrebtii, A. I. (2000). Second-order optical response in semiconductors. Physical Review B, 61(8), 5337.