Crystallography and Properties of Atomic Chirality in Two-dimensional Helical Crystal Tellurium*

Chirality is a fundamental property of nature which is extensively studied in various of fields such as chemistry, material science and biology. In condensed matter physics, chiral crystals bring exotic optical, electrical and magneto properties due to the lack of mirror and inversion symmetry. Tellurium (Te) as one of the chiral materials is formed by van der Waals interaction between each one-dimensional helical chiral atom chains which determine the chirality of the whole crystal, and Te with opposite chiralities are described by different space groups: P3₁21 (right-handed) and P3₂21 (left-handed). Here we report that two dimensional tellurium twin flakes were identified with opposite chirality by electron crystallographic techniques (high-resolution transmission electron microscope image along different primary axes) and sulfuric acid etching method. These Te twin flakes offers an ideal platform to study the chirality-dependent material properties which can potentially be distinguished in electronic structure and transport properties. Our results pave a way for the research in fundamental properties of chiral materials in two-dimensional limit.