A simple and beautiful pattern occurs when light is shined through a pair of slightly misaligned periodic structures. This phenomenon is called the moiré effect, which looks pretty and has significant consequences for the properties of materials.
Moiré patterns in nanomaterials emerge when two atomic layers are slightly rotated relative to each other, creating intricate interference patterns. Typically, these angle adjustments are minimal.
However, researchers in a new study discovered that when they experimented with larger twist angles, unexpected phenomena arose—potentially altering the material’s optical, electronic, or mechanical properties in fascinating ways.
The material’s structure influences this phenomenon. Tungsten ditelluride has an unusual crystal design consisting of distorted quadrilaterals instead of a regular honeycomb pattern.
Researchers from the Institute of Industrial Science at the University of Tokyo have discovered a previously unseen moiré pattern: a series of periodic one-dimensional bands in tungsten ditelluride bilayers.
The resulting pattern is a series of parallel stripes. Typical interference patterns look like two-dimensional arrays of bright spots. These one-dimensional bands are completely distinct from all previously known patterns.
Scientists created a one-dimensional gas out of light
Tomoki Machida, senior author, said, “A more disordered lattice means fewer constraints on the twist angle. By choosing to study this material, we are free to explore the patterns that emerge when the angle is increased significantly.”
The team used theoretical modeling and transmission electron microscopy to pinpoint the exact twist angles—61.767º and 58.264º—where one-dimensional bands emerge. Even a tiny shift, as small as one-tenth of a degree, disrupts this phenomenon, causing the interference pattern to revert to its typical bright spots.
Researchers noted, “Other materials also possess similar one-dimensional patterns at large twist angles. We are currently searching for them and devising ways to apply this very to the study of one-dimensional phenomena. Regardless of what we found, more interesting interference patterns are almost certain to follow.”
Journal Reference
- Xiaohan YangYijin Zhang*Limi ChenKohei AsoWataru YamamoriRai Moriya et al. Intrinsic One-Dimensional Moiré Superlattice in Large-Angle Twisted Bilayer WTe2. ACS Nano. DOI: 10.1021/acsnano.4c17317
