Fig. 2

Mechanism of peak splitting. a, b Peak splitting in the coordinate space for first and second focusing peaks, respectively. The red and white arrows represent spin-up and spin-down electrons, the coloured blocks stand for the electrostatic potential and the red-dashed trace is with smaller cyclotron radius while the yellow-dotted one is with larger cyclotron radius. c, d Peak splitting in the k-space for the first and second focusing peaks, respectively. The electrons travel from (0, k _y ) to (-k _x , 0) anticlockwise in plot (c). In plot (d), the thick blue arrow highlights the transition after reflection at the boundary of electrostatic potential formed between the injector and detector