Moiré superlattices formed by stacking single-layer materials in a twisted configuration can host many exotic states. However, such structures have been found to be disordered, with the twist angle and strain varying unpredictably within a single sample. Kapfer et al. found an elegant method for controlling the twist angle and decreasing the disorder (see the Perspective by Park). The researchers placed a ribbon-shaped graphene layer on top of hexagonal boron nitride and bent one end of the ribbon using the tip of an atomic force microscope. The resulting structure had a twist angle that increased continuously from the point at which the ribbon started bending to its end. Such control is expected to improve reproducibility and understanding of this class of materials. —Jelena Stajic.
Author contributions: M.K., B.S.J., M.E.E., and C.R.D. wrote the manuscript, with input from all authors. M.K., B.S.J., and N.R.F. prepared the graphene devices and performed AFM, PFM, and LFM measurements, and M.K. and B.S.J. analyzed the data. T.P.D. performed Raman measurements, and T.P.D., B.S.J., and M.K. analyzed the data. M.E.E. prepared the TMD device. M.F. and S.L.M. performed nanoPL measurements and together with M.E.E. analyzed the data. D.R.D. calculated the critical buckling strain. B.S.J., M.K., M.F., D.R.D., and A.K.M. did the beam bending calculations. B.S.J. and M.K. prepared samples for nanoARPES; P.M., Z.J., S.U., B.S.J., M.K., D.B., J.A., and P.D. performed the measurements; and P.M., Z.J., and S.U. analyzed the data. V.H. assisted with LFM measurements. K.W. and T.T. grew and provided the hBN crystals.
Link - https://www.science.org/doi/10.1126/science.ade9995