Extended Data Fig. 9: Circular dichroism.
From: Spin-polarized spatially indirect excitons in a topological insulator
a, Sum of non-equilibrium ARPES spectrum of energy versus momentum cut along \(\bar{\Gamma }-\bar{{\rm{M}}}\) measured at time delay 2 ps with the left (CL) and right circularly polarized photons (CR). The color scale in the gray dashed area is enhanced. The black dashed lines are guide for the eye, representing the bulk conduction band and the TSS-bulk continuum. b,c, Circular dichroism (CD) for for delay time 2 ps (b) and 10 ps (c), obtained by (CL − CR)/(CL + CR). The black arrow indicates the location of the bulk state. The black dashed lines in b are guide for the eye, representing the bulk conduction band and the TSS-bulk continuum. The black circle in panel c indicates the observed intensity buildup. d,e, The sum spectrum (CL + CR) (d) and the CD spectrum (CL − CR)/(CL + CR) (e), focusing on the bulk conduction band and the bulk-TSS connection (see the gray dashed square in panel a at time delay 2 ps. The black dashed lines are guide for the eye, representing the bulk conduction band and the TSS-bulk continuum. f, The CD spectra at time delay 10 ps with enhanced color scale, focusing on the exciton intensity buildup.
