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Observation of Strong Nonreciprocal Thermal Emission
Zhenong Zhang1, Alireza Kalantari Dehaghi1, Pramit Ghosh1
1The Pennsylvania State University, Department of Mechanical Engineering, University Park, Pennsylvania 16802, USA.
Physical Review Letters
|July 31, 2025
Summary
Researchers demonstrate strong nonreciprocal thermal emission, breaking Kirchhoff
Area of Science:
- Thermodynamics and Photonics
- Metamaterials and Nanophotonics
Background:
- Kirchhoff's law governs thermal radiation, equating emissivity and absorptivity.
- Strong nonreciprocal thermal emission is crucial for advanced applications but experimentally elusive.
Purpose of the Study:
- To experimentally realize strong nonreciprocal thermal emission.
- To investigate the breaking of Kirchhoff's law in thermal emission.
Main Methods:
- Utilized custom-designed angle-resolved magnetic thermal emission spectroscopy.
- Employed an epitaxially transferred gradient-doped metamaterial.
Main Results:
- Observed strong nonreciprocal thermal emission under a magnetic field.
- Demonstrated a significant difference (up to 0.43) between emissivity and absorptivity, breaking Kirchhoff's law.
- Achieved persistent nonreciprocal emission across broad spectral and angular ranges.
Conclusions:
- The study successfully demonstrates strong nonreciprocal thermal emission.
- The developed approach enables exploration of nonreciprocal thermal photonics for thermal management, infrared camouflage, and energy conversion.
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