Kretschmann-geometry enhancement of a photonic spin Hall effect with an AlCuFe Dirac semimetal

Abstract

We numerically demonstrate a giant and reconfigurable photonic spin Hall effect (PSHE) in a lithography-free Kretschmann stack composed of a high-index prism/AlCuFe Dirac semimetal (DSM)/VO₂/ZnS. By tuning the ZnS coupler thickness to phase-match the input beam with a leaky interfacial mode of the thin DSM film, the p-polarized Fresnel coefficient develops a deep resonance while the s-channel remains finite. Under the near-dark-port conditions, the ratio between the magnitudes of the Fresnel reflection coefficients for the two orthogonal polarizations drives |r_s|/|r_p| (or |r_p|/|r_s|) as large as 10³–10⁴, producing an extremely steep reflection phase and hence macroscopic spin-dependent lateral shifts. With only 50–300 nm of AlCuFe, the peak transverse displacement |δ⁺| reaches 10² μm within narrow angular windows, while off-resonant shifts collapse toward zero. The intermediate VO₂ spacer provides powerful reconfigurability: switching between insulating and metallic phases (and varying its thickness) translates and reshapes the resonance, enabling sign-programmable and angle-tunable PSHE. These results establish a compact, wafer-compatible route to giant spin–orbit photonics – suited for spin-selective beam steering, chiral sensing, and weak-value-style metrology – using only planar films and phase-change control, without nanofabricated structures.