Spectrally selective circular dichroism through resonant tunneling in Weyl-semimetal-based heterostacks

Abstract

We demonstrate that Weyl-semimetal (WSM)/dielectric/WSM heterostacks enable spectrally selective, large circular dichroism (CD) through helicity-selective resonant tunneling. The platform consists of two finite WSM claddings symmetrically sandwiching a high-index dielectric spacer. Time-reversal-broken WSMs host pairs of Weyl nodes separated by 2b in momentum space, yielding an intrinsic anomalous Hall conductivity that splits the circular-polarization eigenchannels. When one helicity is tuned to a high-Q cavity-tunneling resonance while the opposite helicity remains detuned, the device exhibits near-unity CD and a dissymmetry factor approaching |g| → 2 at targeted wavelengths. Thickness-angle maps identify practical control knobs: the spacer thickness l₂ fixes the Fabry–Pérot order and Q-factor. The WSM thickness l₁ sets the helicity-dependent interfacial phase and loading via effective sheet admittance; and the incidence angle θ can pin resonant valleys when the gyrotropic phase dispersion compensates the Fabry–Pérot term. Electrostatic tuning of the carrier density (Fermi energy μ) reconfigures the spectra and reverses handedness. These results establish WSM heterostacks as compact, magnet-free building blocks for narrowband circular polarizers, chiral mirrors, and polarization-selective filters across the mid- to long-wave infrared.