Moiré Hyperbolic Metasurfaces

Abstract

Recent advances in twistronics of low-dimensional materials, such as bilayer graphene and transition-metal dichalcogenides, have enabled a plethora of unusual phenomena associated with moiré physics. However, several of these effects require demanding manipulation of superlattices at the atomic scale, such as the careful control of rotation angle between two closely spaced atomic lattices. Here, we study moiré hyperbolic plasmons in pairs of hyperbolic metasurfaces (HMTSs), unveiling analogous phenomena at the mesoscopic scale. HMTSs are known to support confined surface waves collimated towards specific directions determined by the metasurface dispersion. By rotating two evanescently coupled HMTSs with respect to one another, we unveil rich dispersion engineering, topological transitions at magic angles, broadband field canalization, and plasmon spin-Hall phenomena. These findings open remarkable opportunities to advance metasurface optics, enriching it with moiré physics and twistronic concepts.

Edge-oriented and steerable hyperbolic polaritons in anisotropic van der Waals nanocavities

“…4h are presented in Supplementary Fig. 8, which conforms to analytical dispersions of in-plane hyperbolic sheets 28,34 . Besides, the open angle of the hyperbola gradually increases when the working frequency increases, as the in-plane anisotropy becomes stronger.…”

“…This angle also indicates the direction of the wavevector, as shown in the isofrequency dispersion ( Fig. 1b) 27,28,34 , as the wavevector direction is normal to the edge. We also define the open angle of the hyperbolic dispersion as σ.…”

Polariton panorama

“…These modes exist over a range of frequencies where the in-plane permittivity and the out-of-plane (c-axis) permittivity are of the opposite sign. Hyperbolic electrodynamics and hyperbolic polaritons can originate from a variety of physical processes including phonons [219,223,[228][229][230][231][232][233][234][235][236][237] intersubband transitions in quantum wells [238][239][240] plasmons [220,226,[241][242][243][244], excitons [245], and Cooper pairs (see Cooper pair polaritons). Hyperbolic polaritons dramatically enhance the local photonic density of states and are predicted to give rise to strong nonlinearities [246].…”

Thermal switch with multiple discrete levels

“…Meanwhile, as the gap distance increases, the accuracy of EMT can be further improved. Accord to EMT, this technique is based on modeling the strip near-field coupling as an effective capacitance [43,44]…”