Tuning the untunable: Dirac waves gain new control in terahertz devices

The article discusses a breakthrough in controlling Dirac plasmon polaritons (DPPs), exotic waves that combine light with electron motion in ultra-thin materials, specifically in the terahertz (THz) frequency range. THz waves, which lie between microwaves and infrared light, have long been difficult to harness due to rapid energy loss and poor controllability. The researchers addressed this by using topological insulator metamaterials made from epitaxial Bi2Se3, which conduct electricity only on their surfaces, allowing electrons to behave as massless particles. By designing laterally coupled nanostructures ("metaelements") and precisely adjusting their spacing, they successfully tuned the DPPs’ behavior, increasing the polariton wavevector by up to 20% and extending the attenuation length by over 50%, enabling tighter light confinement and longer propagation with less energy loss. This advancement paves the way for more efficient, tunable THz photonic devices with broad applications, including