Hernández-Martínez, Pedro Ludwig, Sharma, Manoj, Demir, Hilmi Volkan, School of Electrical and Electronic Engineering, School of Materials Science and Engineering, School of Physical and Mathematical Sciences, LUMINOUS! Center of Excellence for Semiconductor Lighting and Displays
In two-dimensional (2D) colloidal semiconductor nanoplatelets, which are atomically flat nanocrystals, the precise control of thickness and composition on the atomic scale allows for the synthesis of heterostructures with well-defined electron and hole wave function distributions. Introducing transition metal dopants with a monolayer precision enables tailored magnetic exchange interactions between dopants and band states. Here, we use the absorption based technique of magnetic circular dichroism (MCD) to directly prove the exchange coupling of magnetic dopants with the band charge carriers in hetero-nanoplatelets with CdSe core and manganese-doped CdS shell (CdSe/Mn:CdS). We show that the strength of both the electron as well as the hole exchange interactions with the dopants can be tuned by varying the nanoplatelets architecture with monolayer accuracy. As MCD is highly sensitive for excitonic resonances, excited level spectroscopy allows us to resolve and identify, in combination with wave function calculations, several excited state transitions including spin-orbit split-off excitonic contributions. Thus, our study not only demonstrates the possibility to expand the extraordinary physical properties of colloidal nanoplatelets toward magneto-optical functionality by transition metal doping but also provides an insight into the excited state electronic structure in this novel two-dimensional material. National Research Foundation (NRF) Accepted version This research is supported by the German Research Foundation DFG under contract BA-1422 and the National Research Foundation, Prime Minister’s Office, Singapore under its Investigatorship program (NRF-NRFI2016-08). H.V.D. gratefully acknowledges TUBA.