Fig. 4: Reversible switching of chiral CDW superlattice induced by an external electric field.
a–c Large-scale STM images of the reversible switching of chiral CDW superlattice of a 1T-NbSe2 island, realized by applying voltage pulses. Two CDW close-packed directions are represented by green and blue arrows, respectively, which are rotated around ±14° with respect to the island edges (labeled by the white dashed double arrows). d–f Magnified images of the areas in (a–c), showing the chirality identified by the relative arrangement of neighboring triangular SOD clusters. The top-layer Se close-packed direction is marked by the black dashed-arrow. g Schematic of the experimental setup. The bias voltage is applied between the tip and the substrate to form an external electric field. h Vth (magnitude of threshold voltage to switch the chirality of CDW) as a function of the lateral distance. The linear fit indicates an electric field effect (0.380 ± 0.016 V/nm) during the chirality switching. The error bar on each point gives the deviation from multiple measurements, which is too small to display. Scanning parameters: a–f, −1.5 V, 20 pA.
