  Chirality manifests in various forms in nature. However, there is no evidence
of the chirality in one-dimensional charge density wave (CDW) systems. Here, we
have explored the chirality among quasi-one-dimensional CDW ground states with
the aid of scanning tunneling microscopy, symmetry analysis, and density
functional theory calculations. We discovered three distinct chiralities
emerging in the form of two-dimensional chiral stacking orders composed of
degenerate CDW ground states: right-, left-, and nonchiral stacking orders.
Such chiral stacking orders correspond to newly introduced chiral winding
numbers. Furthermore, we observed that these chiral stacking orders are
intertwined with chiral vortices and chiral domain walls, which play a crucial
role in engineering the chiral stacking orders. Our findings suggest that the
unexpected chiral stacking orders can open a way to investigate the chirality
in CDW systems, which can lead to diverse phenomena such as circular dichroism
depending on chirality.

Mesoscale and Nanoscale Physics