Enhanced enantiomer discrimination with chiral surface plasmons

Abstract

Strong light-matter coupling in chiral cavities has been proposed as an effective way to selectively interact with an enantiomer that shares the same handedness as the cavity's chiral mode. We show that surface plasmons supported by a two-dimensional interface with both electric and chiral conductivities discriminate enantiomers more efficiently than chiral optical cavities. A quantum-electrodynamic treatment is developed to incorporate the molecule's electric and magnetic dipole moments. We show that the discrimination factor for a chiral plasmon can exceed that of the best chiral-mirror cavity by almost an order of magnitude due to stronger field confinement. In addition, surface plasmons couple to a dipole's projection onto an entire plane, whereas cavity (or free-space) modes couple only to a single polarization axis. This geometric difference produces a $\sqrt{2}$ orientation-averaged boost in chiral discrimination for chiral surface platforms. A handedness-preserving reflector further amplifies the enhancement, opening a practical route towards chiral sensing using twisted-layer platforms.