Edge Plasmons in Two-Component Electron Liquids in the Presence of Pseudomagnetic Fields

Quantum Internal Structure of Plasmons

Plasmons are usually described in terms of macroscopic quantities such as electric fields and currents. However, as fundamental excitations of metals, they are also quantum objects with internal structure. We demonstrate that this can induce an intrinsic dipole moment which is tied to the quantum geometry of the Hilbert space of plasmon states. This quantum geometric dipole offers a unique handle for manipulation of plasmon dynamics via density modulations and electric fields. As a concrete example, we demonstrate that scattering of plasmons with a nonvanishing quantum geometric dipole from impurities is nonreciprocal, skewing in different directions in a valley-dependent fashion. This internal structure can be used to control plasmon trajectories in two dimensional materials.

Plasmonic Nonreciprocity Driven by Band Hybridization in Moiré Materials

We propose a new current-driven mechanism for achieving significant plasmon dispersion nonreciprocity in systems with narrow, strongly hybridized electron bands. The magnitude of the effect is controlled by the strength of electron-electron interactions α, which leads to its particular prominence in moiré materials, characterized by α≫1. Moreover, this phenomenon is most evident in the regime where Landau damping is quenched and plasmon lifetime is increased. The synergy of these two effects holds great promise for novel optoelectronic applications of moiré materials.

Multiple harmonics control of edge pseudomagnetoplasmons in strained grapheme

Valley-resolved edge plasmons are relevant to nano-optics at subwavelength scales. However, less attention has been paid to their tunable properties in time domain. In this work we investigate edge pseudomagnetoplasmons in a strained graphene modulated by multiple harmonics with frequency in the THz regime. The edge plasmon is described by a set of nonlinear hydrodynamic equations, which are self-consistently solved by the flux-corrected transport method. Without the applied voltage, there exist two unidirectional-propagating edge-plasmon modes with weak valley polarization P. It is demonstrated that by varying the amplitude of multiple harmonics one can alter both the amplitude and the polarity of the valley polarization in the edge plasmon. One can achieve a full valley polarization P=1 at the instant of half cycle of the multiple harmonics and P=-1 at the instant of one cycle. The edge-plasmon density and the transverse velocity vanish for the frozen valley.

Long-Lived Domain Wall Plasmons in Gapped Bilayer Graphene

Topological domain walls in dual-gated gapped bilayer graphene host edge states that are gate-tunable and valley polarized. Here we predict that plasmonic collective modes can propagate along these topological domain walls even at zero bulk density and possess a markedly different character from that of bulk plasmons. Strikingly, domain wall plasmons are extremely long-lived with plasmon lifetimes that can be orders of magnitude larger than the transport scattering time in the bulk at low temperatures. Importantly, long domain wall plasmon lifetimes persist even at room temperature with values up to a few picoseconds. Domain wall plasmons possess a rich phenomenology including plasmon oscillation over a wide range of frequencies (up to the mid-infrared), tunable subwavelength electromagnetic confinement lengths, as well as a valley polarization for forward/backward propagating modes. Its unusual features render them as a new tool for realizing low-dissipation plasmonics that transcend the restrictions of the bulk.