Strain-induced topological transitions in black phosphorus metasurfaces for modulating near-field radiative heat transfer

We demonstrate the strain-induced hyperbolic–elliptic topological transition in the near-field radiative heat transfer based on black phosphorus metasurfaces. By applying tensile strain in the zigzag (ZZ) direction, the polariton dispersion shows an extreme in-plane transition—from open hyperbolic to closed elliptic, associated with dramatical modulation effects on the heat flux. First-principles calculations show that a 6% ZZ tensile strain drives an effective-mass switch of electrons along the two crystal axes, which alters the anisotropy conductivity and triggers dispersion transitions. As a result, radiative channels in both frequency and momentum space are redistributed. The transition behavior can be further tuned by varying the tensile strain and electron doping concentration. Furthermore, the strain-induced modulation remains robust over a wide range of metasurface geometries, including different grating periods and filling factors. The proposed structure provides a compact framework for controlling nanoscale thermal radiation via strain-engineered dispersion tailoring in anisotropic two-dimensional systems.