Figure 2: Origin of the circular photo-galvanic effect in lead sulfide nanosheets.
From: Towards colloidal spintronics through Rashba spin-orbit interaction in lead sulphide nanosheets
(a) The generated CPGE by shadowing different positions of the device, and with different illumination angles. The blue and the red lines represent the high and the low illumination angles respectively. The letters indicate the position of the centre of the shadow. The contribution of the vertical asymmetry and the enhanced in-plane asymmetry can be observed (Ivertical and Iin-plane). The inset is a schematic top view of the device to illustrate the position of the shadow during the experiment. In position D the whole device is covered, in C and E half of the device (Ishadow), and A, B, F, and G represent the full illumination of the device (Ifull). (b) Illustration of the possible selection mechanism for exciting the carriers over the band gap. Illumination of the PbS crystal with circularly polarized light leads to transitions in both valleys but excitation of only one spin orientation. (kM,M’: momentum of the excited carriers in a valley). Here, the angular momentum of exciting photons is −1, which is added to the spin-angular momentum of electrons. The states are labeled as |J,M_J>.
