Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session C50: Nano-Plasmonics in Van Der Waals Materials and BeyondInvited
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Sponsoring Units: DCMP Chair: Dmitri Basov |
Monday, March 15, 2021 3:00PM - 3:36PM Live |
C50.00001: Collective modes of twisted van der Waals materials Invited Speaker: Michael Fogler Rotationally misalignment profoundly modifies electronic and lattice properties of van der Waals materials. If the twist angle between adjacent layers is small, a periodic network of dislocations (solitons) delineating large commensurate domains appears. The solitons can have a strong influence on collective modes of the system. A twisted bilayer graphene can act as a photonic crystal for two-dimensional plasmon modes. Propagation of plasmons along one-dimensional links and their scattering at the nodes of the network produces multi-band plasmonic spectra quasiperiodic in frequency. In a twisted boron nitride, the solitons can induce shift and splitting of phonon-polaritons. Our theory and modeling provides explanation for recent nano-optical experiments with twisted van der Waals heterostructures and indicates some possible future directions in this field. |
Monday, March 15, 2021 3:36PM - 4:12PM Live |
C50.00002: Spontaneous out-of-equilibrium plasmonic magnetism in van der Waals materials Invited Speaker: Justin Song Spontaneous symmetry breaking lies at the heart of the description of interacting phases of matter. We will argue that a driven interacting system subject to a linearly polarized (achiral) driving field can spontaneously magnetize (acquire chirality). In particular, we find when a metal (such as graphene) is driven close to its plasmon resonance, it hosts strong internal ac fields that enable Berryogenesis: the spontaneous generation of a self-induced Bloch band Berry flux, which supports and is sustained by a circulating plasmonic motion, even for a linear polarized driving field. This non-equilibrium phase transition occurs above a critical driving amplitude, and depending on system parameters, can enter the spontaneously magnetized state in either a discontinuous or continuous fashion. Berryogenesis relies on nontrivial interband coherences for electronic states near the Fermi energy generated by ac fields readily found in a wide variety of multiband systems. We anticipate that graphene devices, in particular, which can host high quality plasmons, provide a natural and easily available platform to achieve Berryogenesis and spontaneous non-equilibrium (plasmon-mediated) magnetization in present-day devices, e.g., those based on graphene plasmonics. |
Monday, March 15, 2021 4:12PM - 4:48PM Live |
C50.00003: Nanogap Plasmonics for Tailored Properties of 2D Materials Invited Speaker: Maiken Mikkelsen Tailoring light–matter interactions in monolayer MoS2 is critical for its use in optoelectronic and nanophotonic devices. Optical cavities with multiple tunable resonances have the potential to provide unique electromagnetic environments at two or more distinct wavelengths—critical for control of optical processes such as nonlinear generation, entangled photon generation, or photoluminescence (PL) enhancement. Here, we show a plasmonic nanocavity based on a nanopatch antenna design that has two tunable resonant modes in the visible spectrum. The importance of utilizing two resonances simultaneously is demonstrated by integrating monolayer MoS2, a two-dimensional semiconductor, into the colloidally synthesized nanocavities. We observe a 2000-fold enhancement in the PL intensity of MoS2—which has intrinsically low absorption and small quantum yield—at room temperature, enabled by the combination of tailored absorption enhancement at the first harmonic and PL quantum-yield enhancement at the fundamental resonance. Next, we explore how the emission spectrum can be tailored, including complex excitonic states. We demonstrate that the peak emission wavelengths of the A and B excitons can be tuned up to 40 and 25 nm, respectively, by integrating monolayer MoS2 into a plasmonic nanocavity with tunable plasmon resonances. Contrary to the intrinsic photoluminescence spectrum of monolayer MoS2, we are also able to create a dominant B exciton peak when the nanocavity is resonant with its emission. Additionally, we observe a 1200-fold enhancement of the A exciton emission and a 6100-fold enhancement of the B exciton emission when normalized to the area under a single nanocavity and compared to a control sample on thermal oxide. |
Monday, March 15, 2021 4:48PM - 5:24PM Live |
C50.00004: Nano-polaritonics in twisted van der Waals heterostructures Invited Speaker: GuangXin Ni Interlayer coupling in atomic van der Waals heterostructures plays a rather unique role in controlling their optical and electronic properties. The character of the interlayer coupling can be manipulated by a particular stacking arrangement of the proximal layers and by adjusting the orientation of the neighboring planes. The latter method is known to trigger the long-range periodic modulations referred to as twisted moiré superlattices. The presence of periodic moiré patterns enables further fine tuning of the electronic band structure and yielding rich insights into the electronic/optical phenomenon. This has been manifested in graphene/hexagonal boron nitride (G/hBN) moiré patterns, twisted bilayer graphene structures as well as twisted hBN crystals. Using nano-infrared optical microscopy we have experimentally studied the collective excitations in these twisted moiré structures. We analyzed these soliton networks and obtained the local electrodynamical characters based on the infrared active polaritonics at the nanoscale. |
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