Chiral Charge Density Wave and Backscattering-Immune Orbital Texture in Monolayer 1-TiTe.

Nontrivial electronic states are attracting intense attention in low-dimensional physics. Though chirality has been identified in charge states with a scalar order parameter, its intertwining with charge density waves (CDW), film thickness, and the impact on the electronic behaviors remain less well understood. Here, using scanning tunneling microscopy, we report a 2 × 2 chiral CDW as well as a strong suppression of the Te-5 hole-band backscattering in monolayer 1-TiTe. These exotic characters vanish in bilayer TiTe in a non-CDW state. Theoretical calculations prove that chirality comes from a helical stacking of the triple- CDW components and, therefore, can persist at the two-dimensional limit. Furthermore, the chirality renders the Te-5 bands with an unconventional orbital texture that prohibits electron backscattering. Our study establishes TiTe as a promising playground for manipulating the chiral ground states at the monolayer limit and provides a novel path to engineer electronic properties from an orbital degree.