Congratulations to Lauren Barr for her recent Physical Review B publication “Investigating the nature of chiral near-field interactions“. Well done!
Electromagnetic interactions are often stronger in the near-field of an antenna, where the field gradients are largest. This was also thought to be true close to a chiral antenna, where so-called “superchiral” fields can be generated. Using a metasurface of helices, researchers in Exeter investigated interactions with the near fields generated by a chiral antenna. By comparing the experiment to a simple model, they found that, surprisingly, large field gradients did not enhance the chiral interaction.
Objects that lack mirror symmetry are abundant in nature, from sugars to snail-shells to hurricanes. These twisted objects are termed ‘chiral’, and come in left-handed and right-handed varieties. The handedness of sugars and proteins determines how they interact with our bodies, but efficient characterisation is difficult, as scientists have to study their weak interaction with light that has a similar handed (“circular polarised”) character.
Researchers at the University of Exeter used a microwave analogy to chiral molecules, where they were replicated by small metallic helices. The helices act to probe the highly twisted electromagnetic fields close to a source of handed microwaves, and looked for a strong interaction. Alongside, the chiral fields were examined with an equivalent homogeneous material in a numerical simulation. This model purposefully neglected any higher-order interactions between the highly twisted fields and the discrete helices. The simulation and experiment agreed well, meaning that enhancing the chirality of a field does not enhance the strength of a chiral interaction, contrary to previous hypotheses.
