Preprint Demonstrates Chirality Emergence via Conductivity Tensor Rotation in Achiral Plasmonic Rectangles

The arXiv preprint from Magnus Jonsson's group at Linköping University reports experiments with rectangular plasmonic nanoantennas fabricated on an aligned conducting polymer film. By varying the angle between the polymer backbone and the rectangle axes, researchers decoupled the linear responses to generate spin-selective optical output. Carrier density modulation via electrochemical gating further allowed reversible switching between left- and right-handed responses without altering geometry. This setup was tested across multiple rotation angles and doping levels, confirming that optical chirality arises purely from misalignment of the anisotropic conductivity tensor with the nanostructure symmetry. The result directly challenges the long-standing assumption in nanophotonics that geometric chirality or 3D asymmetry is required for strong circular dichroism. Instead, the work shows that independent linear polarizabilities can be engineered to produce effective chirality through conductivity control alone. This enables a single rotational degree of freedom to encode both geometric phase and local optical chirality in metasurface design, simplifying phase-gradient devices that previously needed separate elements for wavefront and polarization control. Contextually, this extends prior work on anisotropic metamaterials and conducting polymers in optoelectronics, where carrier tuning has been used for dynamic phase modulation but not for chirality generation. The approach could impact compact sensors and energy-harvesting metasurfaces by allowing electrically switchable circular polarization selectivity. However, the evidence remains at the proof-of-concept stage with limited spectral range data. Next steps include scaling to visible wavelengths and integrating with CMOS-compatible processes to test durability under repeated gating cycles. Independent replication with different polymer systems would strengthen claims of generality.