How to Make Devices with Weyl Materials

In 2015, physicists discovered a new topological state of matter known as a Weyl semimetal. Electronic excitations in such a material do not behave as nearly free electrons, like in most metals. Instead, they can effectively be described as massless relativistic particles with properties similar to photons. Beside their fundamental interest, the exotic behavior of Weyl fermion materials motivates the pursuit of electronic or optical devices with novel functionalities. Romilly Hills at Loughborough University, UK, and collaborators have now theoretically investigated a range of devices that could be made using such materials [1]. In particular, they propose that a structure made of multiple layers of Weyl semimetals would behave as a medium whose effective refractive index is negative, which could focus a diverging electron beam onto an extremely small region. Such a property could lead to a “superlens” that boosts the spatial resolution of scanning tunneling microscopes (STMs).