Phys.org June 17, 2024 Biomimetic nanotechnology and self-assembly advances need chirality. There is a need to develop general methods to characterize chiral building blocks at the nanoscale in liquids such as water. An international team of researchers (UK, Italy, USA – University of Nebraska, Pennsylvania State University) observed chiroptical second-harmonic Tyndall scattering effect in high-refractive-index dielectric nanomaterial Si nanohelices. They provided a theoretical analysis that explained the origin of the effect and its direction dependence, resulting from different specific contributions of “electric dipole–magnetic dipole” and “electric dipole–electric quadrupole” coupling tensors. They narrowed down the number of such terms to 8 […]
Category Archives: Optical properties
Tiny displacements, giant changes in optical properties
Nanowerk May 7, 2024 It is shown that structural disorder in the form of anisotropic, picoscale atomic displacements modulates the refractive index tensor and results in the giant optical anisotropy observed in BaTiS3. An international team of researchers (University of Southern California, Washington University, University of Wisconsin–Madison, UC Santa Barbara, Lawrence Berkeley National Laboratory, Oak Ridge National Laboratory, Switzerland) used scanning transmission electron microscopy to directly observe the globally disordered Ti a–b plane displacements and found them to be ordered locally over a few unit cells. First-principles calculations showed that the Ti a–b plane displacements selectively reduced the refractive index […]