Hyperbolic Metamaterials with Extreme Mechanical Hardness

Hyperbolic metamaterials (HMMs) are highly anisotropic optical materials that behave as metals or as dielectrics depending on the direction of propagation of light. They are becoming essential for a plethora of applications, ranging from aerospace to automotive, from wireless to medical and IoT. These applications often work in harsh environments or may sustain remarkable external stresses. This calls for materials that show enhanced optical properties as well as tailorable mechanical properties. Depending on their specific use, both hard and ultrasoft materials can be required, although the combination with optical hyperbolic response is rarely addressed. Here, the possibility to combine optical hyperbolicity and tunable mechanical properties in the same (meta)material is demonstrated, focusing on the case of extreme mechanical hardness. Using high-throughput calculations from first principles and effective medium theory, a large class of layered materials with hyperbolic optical activity in the near-IR and visible range is explored, and a reduced number of ultrasoft and hard HMMs is identified among more than 1800 combinations of transition metal rocksalt crystals. Once validated by the experiments, this new class of metamaterials may foster previously unexplored optical/mechanical applications.

Automated summary

Hyperbolic metamaterials (HMMs) are anisotropic optical materials that can behave as metals or dielectrics depending on the direction of light propagation, making them essential for a wide range of applications. The combination of optical hyperbolicity and tunable mechanical properties in the same material is demonstrated, with the potential to foster new optical/mechanical applications. High-throughput calculations and experiments are used to explore a class of layered materials with hyperbolic optical activity and identify ultrasoft and hard HMMs among numerous combinations of transition metal rocksalt crystals.