Optical Wigner crystal lattices enabled by Kekulé metasurfaces

Abstract Wigner crystal (WC) localizes the electrons into a close-packed regular lattice and remains one of the most fragile quantum states since its first prediction in 1934 1 . The evidences of electronic Wigner crystals were observed in liquid helium 2,3 , carbon nanotube 4 , extremely clean GaAs/AlGaAs quantum wells 5–7 , two-dimensional electron gases 8, 9 and various moiré superlattice 10–12 . However, there is limited demonstration of such concepts for photons ( i.e. , polaritons). Here we develop, theoretically and experimentally, an optical analogue of Wigner crystal in a new category of metasurface named as Kekulé metasurface. This plasmonic nanostructure crystalizes surface plasmonic polaritons into assorted Wigner crystal lattice at two-dimensional limit, visualized by noninvasive leakage radiation microscopy. The spatial distribution and relative intensity of Wigner crystal lattice site are tailored and melted by superposing an extra wing-shaped nanoslit set. Configurable on-chip light-emitter array and high-security imaging encryption/decryption using optical Wigner crystal lattices are further demonstrated. This work reports a versatile Kekulé metasurface platform and optical Wigner crystal lattices with multiple degrees of freedoms, featuring rich physic phenomena and potential photonic elements for applications into existing technologies.