Fig. 3: Spatial evolution of CDW pattern and dI/dV spectra across steps.
From: Chirality locking charge density waves in a chiral crystal
a Upper panel, a surface region showing terraces with different indices. Scanning settings: Vs = −1 V, It = 0.6 nA. Lower panel, height profile along the red line in the upper panel, showing sequential steps with half of the lattice constant along c axis. b Schematic drawing of the atomic arrangement of the terraces. The surface atoms on terraces possess n and n + 1/2 indices, and are linked with glide-mirror symmetry. STM image (c) and dI/dV map under zero bias (d) of a region with steps. The height difference between the highest (upper part in (c)) and lowest (lower left part in (c)) terraces is 2 times of the c-axis lattice constant c. The CDW stripes are in phase across even steps, as outlined by red dashed lines. Scanning settings of c: Vs = −200 mV, It = 0.1 nA. STM image (e) and dI/dV map under zero bias (f) of a region with sequential odd steps with heights of 2.5c. The CDW stripes are out of phase across odd steps, as outlined by red and black dashed lines. Scanning settings of (e): Vs = −200 mV, It = 0.1 nA. g STM image of an odd step. Scanning settings: Vs = 500 mV, It = 0.1 nA. h, i, Waterfall plot and intensity map of dI/dV spectra along the dashed arrow in (g). On the lower terrace, the asymmetric CDW coherence peaks show larger spectral weight under positive bias, while under negative bias the spectral weight of the coherence peak gets stronger on the upper terrace. This asymmetry reverses across the odd step.
