  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.
