Fig. 4: Chiroptical spectroscopy of an externally controlled single nanohelix.

a SEM (scale bar 100 nm) and schematics of an Au nanohelix with magnetic moment m (brown segment at end of helix) that will align with respect to an external magnetic field B (black). Forced sampling of isotropic orientations is achieved by evenly distributing points (black dots) on the surface of a sphere. b 〈CDSI〉_t over 10 forced isotropic sampling sequences with i = 100 points (black) and 〈CDSI〉_t of the same particle undergoing Brownian motion (t = 400 frames, red). Thirty randomly selected spectra of individual frames are depicted in the background, whereas the purple vertical line indicates the spectral region shown in (c). c CDSI at λ =  800 ± 5 nm (10 spectra per coordinate) mapped onto the external field coordinates.