Fig. 13

Thermal photonic applications. a A nonreciprocal thermal emitter based on a magnetic Weyl semimetal photonic crystal. b Dispersion of the nonreciprocal surface plasmon polaritons of the Weyl semimetal. The gray region is the light cone of the vacuum. The blue region denotes the continuum of bulk modes. The red region denotes the surface plasmons used for nonreciprocal thermal emission. The gray dashed lines denote the boundaries of the Brillouin zones. \(k_F = E_F/\hbar v_F\) is the Fermi wavevector. c Emissivity and absorptivity spectra in \(\theta = 80^\circ\) direction. d Persistent directional heat current in a many-body system, at the thermal equilibrium of temperature T. The spheres are made of magneto-optical materials, with a magnetic field applied perpendicular to the plane of the triangle. Magnetic Weyl semimetals can provide the same effects without a magnetic field. e The photon thermal Hall effect among four particles made of magnetic Weyl semimetals forming a square with \(C_4\) symmetry. A temperature gradient \(\Delta T\) between particles 1 and 2 along the x-axis induces a nonzero temperature difference between particles 3 and 4. f A radiative thermal router based on three spheres of Weyl semimetal nanoparticles: tuning the Weyl node separation of the center particle will guide the heat to flow in a different direction. Figures are reproduced with permission from (a-c) Ref. [14], Copyright 2020 American Chemical Society; d Ref. [284], Copyright 2016 American Physical Society; e Ref. [290], Copyright 2020 American Physical Society; f Ref. [298], Copyright 2020 American Chemical Society