Fig. 1: STM topography and schematic model of chiral CDW superlattice.
a (upper panel) Top view of SOD model showing thirteen Nb atoms, six top Se atoms, and six bottom Se atoms, with three-fold symmetry; (lower panel) side view of SL 1T-NbSe2 on a BLG/SiC(0001) substrate. The top- and bottom-layer Se atoms are projected from the upper to the lower panel to show the relative positions. b CDW-resolved STM topography around a domain boundary of SL 1T-NbSe2. The top-Se close-packed direction is marked by the black dashed-arrow. c Left (right): Zoomed-in atomic-resolved image in the L (R) domain marked by the green (blue) frame in (b). The SOD superlattices in these two domains are labeled by green and blue triangles, respectively. The SODs arrangements are represented by the clockwise (CW) and counterclockwise (CCW) arrows. d Atomic model of SL 1T-NbSe2 with chiral CDW domains. The atomic lattice of the top layer Se is indicated by the lattice of orange balls, and the SOD clusters in these two domains are labeled by green and blue triangles encircled by hexagram stars, respectively. Green and blue arrows crossing the adjacent SOD triangles represent the chiral CDW close-packed directions, which are rotated by ±14° with respect to the top-layer Se atom close-packed direction (bL1 and bL2 for the L domain, and bR1 and bR2 for the R domain). Scanning parameters: b, bias voltage VB = −1.5 V, tunneling current It = 1 nA; c, VB = −1.5 V, It = 2 nA.
