Chiral charge density waves induced by Ti-doping in 1T-TaS2

TL;DR

This study reveals that Ti-doping in 1T-TaS2 induces a unique chiral charge density wave phase at a specific doping level, linked to doping-enhanced orbital order, expanding understanding of chiral CDW phenomena.

Contribution

It demonstrates the emergence of a chiral CDW phase in Ti-doped 1T-TaS2 at a specific doping concentration, highlighting the role of orbital order and doping element characteristics.

Findings

Chiral CDW appears at x=0.08 Ti-doping.

Ti-doping preserves the electronic flat band.

Orbital order enhancement triggers chirality.

Abstract

We investigate the Ti-doping effect on the charge density wave (CDW) of 1T-TaS2 by combining scanning tunneling microscopy (STM) measurements and first-principle calculations. Although the Ti-doping induced phase evolution seems regular with increasing of the doping concentration (x), an unexpected chiral CDW phase is observed in the sample with x = 0.08, in which Ti atoms almost fully occupy the central Ta atoms in the CDW clusters. The emergence of the chiral CDW is proposed to be from the doping-enhanced orbital order. Only when x = 0.08, the possible long-range orbital order can trigger the chiral CDW phase. Compared with other 3d-elements doped 1T-TaS2, the Ti-doping retains the electronic flat band and the corresponding CDW phase, which is a prerequisite for the emergence of chirality. We expect that introducing elements with a strong orbital character may induce a chiral charge order in a broad class of CDW systems. The present results open up another avenue for further exploring the chiral CDW materials.