US scientists shatter 165-year-old physics rule for energy breakthroughs

A research team at Penn State has reported a groundbreaking violation of Kirchhoff’s law of thermal radiation, a fundamental physics principle established 165 years ago. Kirchhoff’s law states that a material’s ability to absorb energy at a specific wavelength and angle must equal its ability to emit energy under the same conditions. However, the Penn State scientists demonstrated a significant non-reciprocity contrast of 0.43—indicating a notable difference between absorptivity and emissivity—using a specially designed five-layer thin film semiconductor structure. This effect was observed over a broad 10-micrometer wavelength range, marking the strongest recorded deviation from the law’s reciprocity principle. This breakthrough has important implications for energy harvesting and thermal management technologies. For example, conventional solar cells must emit some absorbed energy back to the sun, which limits their efficiency. The new non-reciprocal material can direct emitted energy away from the sun, potentially allowing that energy to be captured by additional solar cells and thus improving overall