Breaking the symmetry of colloidal 2D nanoplatelets: Twist induced quantum coupling

Twist provides a new degree of freedom for nanomaterial modifications, which can provide novel physical properties. Here, colloidal two-dimensional (2D) twisted CdSe nanoplatelets (NPLs) are successfully fabricated and their morphology can change from totally flat to edge-twisted, and then to middle-twisted with prolonged reaction time. By combining experiments and corresponding theoretical analyses, we have established the length-dependent relationships between the surface energy and twist, with a critical lateral dimension of 30 nm. We found that the defects formed during the synthesis process play a vital role in generating intense stress that develops a strong torsion tensor around the edges, resulting in edge-twisted and final middle-twisted NPLs. Furthermore, due to the geometric asymmetry of twisted NPLs, the dissymmetry factor of single particle NPLs can reach up to 0.334. Specifically, quantum coupling occurs in middle-twisted NPLs by twisting one parent NPL into two daughter NPLs, which are structurally and electronically coupled. This work not only further deepens our understanding of the twist mechanism of 2D NPLs during colloidal synthesis, but also opens a pathway for applications using twistronics and quantum technology. [Figure not available: see fulltext.]