Nonreciprocal Hyperbolic and Surface Modes Enable Tunable Near-Field Heat Transfer in Current-Biased Dirac Semimetals

The motion of charge carriers via current bias can create a dragging effect on propagating surface plasmon polaritons (SPPs), a phenomenon known as plasmon Fizeau drag. This effect is predicted to be supported by 3D Dirac semimetals (DSMs) due to their high saturation velocity and mobility. We propose current-biased 3D DSMs as a promising platform for tunable near-field radiative heat transfer. We predict that modulating the magnitude and direction of the current bias in Cd₃As₂, in combination with gating, can achieve on/off switching ratios of up to 22 for gaps of 100 nm, higher than previously explored gate-tunable systems. The superior tunability of our system is attributed to low-loss, nonreciprocal SPPs and dynamic tuning of hyperbolic modes, sensitive to the magnitude and direction of current bias. Finally, we predict that this system supports heat pumping in the absence of a temperature gradient due to the Doppler shift of the photon occupation number.