Dynamically tunable polarized mid-infrared light-emitting diodes from polarization singularities in a band-edge Weyl node.

Abstract

The polarization states of light-emitting devices in conventional semiconductors are typically deterministically fixed by optical transition selection rules. However, in emerging Weyl semiconductors, band-crossing Weyl nodes introduce exotic polarization contrasts, making emission polarization sensitive to carrier dynamics. Here, we demonstrate mid-infrared light-emitting diodes based on van der Waals tellurium, a Weyl semiconductor featuring a Weyl node precisely at the conduction band minimum (CBM). These devices demonstrate high polarization tunability, with linear polarization degrees continuously adjustable from ~100% (low carrier density) to 36% (high carrier density). First-principles calculations reveal that this tunability originates from polarization singularities induced by CBM-located Weyl nodes, where the polarization state is dynamically modulated by the quasi-Fermi level shift and hot-carrier recombination under varying injection densities. Our findings establish band-edge Weyl nodes as a promising platform for tunable polarized emitters and open alternative avenues for topological optoelectronics.