In the growing field of quantum materials, researchers keep finding things that defy expectations. Case in point – a metal capable of conducting light is detailed in a new paper from Columbia University.<\/p>\n
Since most metallic materials are reflective at visible light wavelengths, any light that strikes them will bounce back. Metals are great at moving heat and electricity, but people don’t usually think of them as a way to move light.<\/p>\n
Yinming Shao, a postdoc at Columbia who led the work, has been investigating the optical properties of a semimetal material called ZrSiSe. In a study published in 2020, Shao and his colleagues showed that ZrSiSe and graphene<\/a>, the first “Dirac material” found in 2004, have similar electronic properties. Enhanced electronic correlations, which are uncommon for Dirac semimetals, are present in ZrSiSe.<\/p>\n Graphene is a single, atom-thin layer of carbon, whereas ZrSiSe is a three-dimensional metallic crystal made up of layers that exhibit anisotropy, or different behaviour in the in-plane and out-of-plane directions.<\/p>\n “It’s sort of like a sandwich: One layer acts like a metal while the next layer acts like an insulator. When that happens, light starts to interact unusually with the metal at certain frequencies. Instead of just bouncing off, it can travel inside the material in a zigzag pattern, which we call hyperbolic propagation,”<\/p><\/blockquote>\n said Shao.<\/p>\n Shao and his colleagues from Columbia and the University of California, San Diego saw this zigzag movement of light when they used ZrSiSe samples of different thicknesses. This movement is also called hyperbolic waveguide modes<\/a>.<\/p>\n These waveguides, which here are plasmons, are produced when light photons combine with electron oscillations to form hybrid quasiparticles that can direct light through a material.<\/p>\nHyperbolic Waveguide Modes<\/h2>\n