Nonreciprocal and collimated surface plasmons in drift-biased graphene metasurfaces

Abstract

We explore the unusual non-reciprocal and diffraction-less properties of surface plasmon polaritons propagating in drift-biased graphene-based metasurfaces. We show that applying a drift-current on a graphene sheet leads to extremely asymmetric in-plane modal dispersions from terahertz to infrared frequencies, associated with plasmons with low-loss (high-loss and ultra-high confinement) traveling along (against) the bias. Strikingly, truly unidirectional wave propagation is prevented by the intrinsic nonlocal response of a graphene, a mechanism that shapes the energy flow over the surface. We also show that highly-directive hyperbolic plasmons completely immune to backscattering propagate obliquely along the drift in nanostructured graphene. Finally, we discuss how spin-orbit interactions can be exploited in this platform to efficiently launch collimated plasmons along a single direction while maintaining giant non-reciprocal responses. Our findings open a new paradigm to excite, collimate, steer, and process surface plasmons over a broad frequency band. PACS: 32.10.Dk, 42.25.Fx, 73.20.Mf, 78.67.Wj The Lorentz reciprocity principle constrains the performance of photonic systems by enforcing identical responses when observation and excitation points are interchanged [1][2][3][4]. Recently, nonreciprocal surface plasmons-polaritons (SPPs) have merged the concept of one-wave optical propagation with the confinement and manipulation of light in engineered surfaces much smaller than the wavelength [5][6][7][8][9][10]. The possibility to collimate and dynamically control the direction of these waves within a surface opens exciting venues to realize miniaturized all-photonic integrated systems [11] and may enable new applications in sub-diffractive nanophotonics, including sensing, imaging, and computing. Even though

Electromagnetic Wave Scattering from a Moving Medium with Stationary Interface across the Interluminal Regime

“…The experimental implementation of the problem solved in the paper seems challenging given the relativistic velocities of the fluid at the high end of the subluminal regimes and in the interluminal regimes, even if one would resort to the latest fluid dynamics technologies. However, the fluid could be potentially replaced by flows of electrons in naturally bounded two-dimensional plasmonic structures [32,33]. Moreover, spacetime perturbations, i.e., modulations without transfer of matter, of relativistic velocities are perfectly attainable in practice, and are directly related to the problem studied here by Lorentz transformations.…”

Nonreciprocal and Topological Plasmonics

“…Another interesting approach that has received recent attention in the literature is based on biasing a conducting material with a direct electric current J DC , which, just like the magnetic field, is also a physical quantity with odd symmetry under time reversal, and therefore it can be used to break Lorentz reciprocity [80][81][82]. In particular, the forced drift movement of free electrons in the conducting material produces a Doppler shift such that the frequency ω in the dispersive material permittivity changes to ω − k u, where u is the electron drift velocity and k is the wavenumber of an electromagnetic wave propagating in the current direction.…”

Acoustically driven Dirac electrons in monolayer graphene

“…A significant plasmonic Doppler effect can emerge in electrically biased graphene when the electron drift velocity v d reaches a substantial fraction of the plasmon velocity 18,23 . Such a Doppler effect has been predicted to break the time reversal symmetry in the graphene optical response in the nonlocal limit and create non-reciprocal surface plasmon propagations [24][25][26][27][28][29][30][31] .…”