Chiral Charge Density Wave and Backscattering-Immune Orbital Texture in Monolayer 1<i>T</i>-TiTe<sub>2</sub>.

Ren, Mingqiang; Cheng, Fangjun; Zhao, Yufei; Gu, Mingqiang; Cheng, Qiangjun; Yan, Binghai; Liu, Qihang; Ma, Xucun et al. · Nano Lett · 2023

basic_science · Level V

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Abstract

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<i>p</i> hole-band backscattering in monolayer 1<i>T</i>-TiTe<sub>2</sub>. These exotic characters vanish in bilayer TiTe<sub>2</sub> in a non-CDW state. Theoretical calculations prove that chirality comes from a helical stacking of the triple-<i>q</i> CDW components and, therefore, can persist at the two-dimensional limit. Furthermore, the chirality renders the Te-5<i>p</i> bands with an unconventional orbital texture that prohibits electron backscattering. Our study establishes TiTe<sub>2</sub> 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.