Measurement of the surface susceptibility of single-layer atomic crystal by the photonic spin Hall effect in momentum space

Fast and robust measurement of the surface susceptibility is still in urgent need for investigation and application of atomically thin crystals. In this work, we propose an effective method to measure the surface susceptibility of single-layer graphene by detecting the photonic spin Hall effect in momentum space. At a graphene interface, the beam separations with different spin states contain an angular component due to the existence of surface susceptibility. By implementing a postselection with real weak value in our scheme, the contribution of the spatial spin-Hall shift is excluded and the angular one is amplified for detection. It is demonstrated that treating the angular shift as a pointer allows for a reliable determination of the surface susceptibility. Our method may pave a way for the optical parameter characterization of two-dimensional atomic crystals via angular metrology.