Fig. 6

Broken reciprocity in thermal photonics by using magneto-optical effect. a MO grating enables the near-complete violation of detailed balance between α and e. b Incident angle-resolved nonreciprocal absorption phenomenon measured from Si grating loaded highly-doped InAs structures. Circles and error bars denote the maximum absorption and the 5% variation wavelength range from maximum absorption, respectively. c Berreman mode induced a large violation of Kirchhoff’s law in ultrathin InAs films at ENZ wavelengths. d A MO material-based nonreciprocal grating with a compound symmetry that illustrates the adjoint Kirchhoff’s law. e Persistent heat current generated in a nonreciprocal many-body system at thermal equilibrium. f Photon thermal Hall effect in a nonreciprocal many-body system. The transverse temperature difference is formed when the many-body system is magnetized. Figures adapted from: a, ref [114]; b, ref [123]; c, ref [128]; d, ref [10]; e, ref [135]; f, ref [141]