Science Daily March 4, 2021
A hot topic in the field of 2D materials has been exploring how twisting can change the electronic properties of the layered system. van der Waals (vdW) heterostructures feature layers that can be stacked at arbitrary angles, giving complete control over the presence or lack of inversion symmetry at a crystal interface. An international team of researchers (USA – Columbia University, industry, Germany, Japan) demonstrated highly tunable second harmonic generation (SHG) using bulk hexagonal boron nitride crystals and introduced the term twistoptics to describe studies of optical properties in twistable vdW systems. By suppressing residual bulk effects, they were able to modulate SHG intensity by a factor of more than 50, and polarization patterns determined by moiré interface symmetry. They demonstrated greatly enhanced conversion efficiency in vdW vertical superlattice structures with multiple symmetry-broken interfaces. The study could provide a compact means for generating entangled photons and single photons for next-generation optical quantum information processing and computing….read more. Open Access TECHNICAL ARTICLE
SHG from bulk BN crystals and homostructures. Credit: Science Advances 03 Mar 2021: Vol. 7, no. 10, eabe8691