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 V25: Chemical Physics in Strong Fields IILive
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Sponsoring Units: DCP Chair: Albert Stolow, Univ of Ottawa |
Thursday, March 18, 2021 3:00PM - 3:12PM Live |
V25.00001: Theory-Guided Identification and Development of Plasmonic Spinel Oxides Steven Hartman, Ekaterina Dolgopolova, Jennifer A Hollingsworth, Ghanshyam Pilania Plasmonic materials use standing electron waves, called plasmons, to interact with incoming light. While metals can be good plasmonics, their frequency response depends on the concentration of free charge carriers which is difficult to control, so metal-based plasmonics are usually limited to the visible spectrum. To create tunable IR-active plasmonic materials, we want to find semiconductors that achieve either n- or p-type (but not both simultaneously) conduction via doping. Recent experiments show that the inverse spinels Fe3O4 and Ga2FeO4 meet these criteria, but the underlying reasons are poorly understood. |
Thursday, March 18, 2021 3:12PM - 3:24PM Live |
V25.00002: Optically Controlling Femtosecond Hot Electron Spatial and Momentum Distributions in Nanoplasmonic Systems Jacob Pettine, Priscilla Choo, Sean M Meyer, Fabio Medeghini, Teri W. Odom, Catherine J. Murphy, David John Nesbitt Plasmonic metal nanoparticles concentrate optical field energy into deeply sub-wavelength volumes, producing high densities of excited (hot) electrons and holes. While predicting and controlling the spatial and momentum distributions of these hot carriers remain significant challenges, such capabilities introduce exciting opportunities for actively controlling ultrafast currents in a variety of photocatalytic, photovoltaic, and integrated nanophotonic applications. Toward these ends, a few vignettes from recent single-nanoparticle angle-resolved photoemission spectroscopy studies will be presented. Gold nanostars, for instance, behave as multi-tip photocathodes with simultaneous frequency- and polarization-selective tip hot spots for photocurrent directionality control. Gold nanorods, on the other hand, provide a unique testbed for distinguishing fundamental surface- vs. volume-mediated photoemission pathways and their corresponding hot electron spatial/momentum distributions. These investigations are complemented by a combination of classical finite element electrodynamics, semi-classical Monte Carlo, and fully quantum modeling for predictively understanding hot electron dynamics in arbitrary nanoplasmonic geometries. |
Thursday, March 18, 2021 3:24PM - 3:36PM Live |
V25.00003: Thermal effects - an alternative mechanism for plasmonic-assisted photo-catalysis Yonatan Sivan, Yonatan Dubi, Ieng-Wai Un Recent experimental studies demonstrated that chemical reactions can be accelerated by adding metal nanoparticles to the chemical reactants and illuminate them at their plasmon resonance. It was claimed that the enhanced reaction rate occurs via the reduction in the activation energy driven by the plasmon-induced non-thermal (“hot”) electrons. In this contribution, we show that these claims are extremely unlikely to be correct and that instead, the faster chemical reactions are likely the result of mere heating. To do that, we derive a self-consistent theory of the electron distribution in metal nanostructures under continuous-wave illumination. We show [Dubi & Sivan, Light Sci. Appl., 2019] that only about one-billionth of the energy provided by the illumination goes to creating non-thermal (“hot”) electrons, and the rest goes to heating. Further, we develop a simple model based on the Fermi golden rule and the Arrhenius Law. We show [Sivan et al., Science, 2019; Dubi et al., Chem. Sci., 2020] that the alternative theory of illumination-induced heating can explain the experimental data to a remarkable agreement. Our results provide the first-ever comprehensive theory of plasmon-assisted photocatalysis and should become the basis for the analysis of future experiments. |
Thursday, March 18, 2021 3:36PM - 3:48PM Live |
V25.00004: The Electromagnetic Enhancement of SERS and the Modified Partition of Optical States in the Strong Matter-Coupling Regime. Kritika Jain, Murugesan Venkatapathi Surface enhanced Raman Spectroscopy (SERS) is a powerful optical sensing technique that is based on enhanced Raman signals from molecules in proximity of rough metal surfaces. Experiments1 have shown unexpected large enhancements in SERS, even up to 1014. Conventional electromagnetic theory accounts for enhancements only up to 106, and the anomalous enhancements have been sometimes attributed to an unknown chemical origin2. We highlight the need for a modification to the conventional partition of optical states in the case of an emitter strongly coupled to absorbing matter, and such high gains can be inferred as the result of tunneling out of photons from the strongly absorbing metal surface. This modification to the conventional partition of optical states into its radiative and non-radiative parts, is also imperative for emitters proximal to limiting small metal nanoparticles (< 10 nm in dimensions) which are fully absorbing and do not scatter light3,4. This effect can be exploited further in light generation, optical sensing and radiative heat transfer. |
Thursday, March 18, 2021 3:48PM - 4:00PM Live |
V25.00005: Second-harmonic generation in plasmonic lattices enhanced by quantum emitter gain Andrei Piryatinski, Oleksiy Roslyak, Maxim Sukharev The nonlinear optics of plasmonic nanostructures has become a hot research field. Applications range from optical bi-stability to second harmonic generation (SHG). We report on theoretical study of SHG in plasmonic lattices interacting with quantum emitters (QE) under incoherent energy pump. We generalize driven-dissipative Tavis-Cummings model by introducing anharmonic surface-plasmon mode and examine polariton modes in strong (lasing) coupling regime. Subsequent calculations of the SHG efficiency show strong enhancement due to polariton gain. We further discuss time-domain numerical simulations of SHG in 2D lattice of Ag nano-pillars coupled to QEs utilizing fully vectorial nonlinear hydrodynamic model for conduction electrons coupled to Maxwell-Bloch equations for QEs. The simulations clearly show orders of magnitude increase in the SHG efficiency as the QEs are tuned in resonance with the lattice plasmon mode and brought above the population inversion threshold by incoherent pump. By varying pump frequency and tuning QEs to a localized plasmon mode, we demonstrate further enhancement of the SHG efficiency facilitated by strong local electric fields. The incident light polarization dependance of the SHG is examined and related to the symmetries of participating plasmon modes. |
Thursday, March 18, 2021 4:00PM - 4:12PM Live |
V25.00006: Atomistic Understanding of Plasmon Mediated Photochemical Reactions Yu Zhang Localized surface plasmon resonances (LSPRs) have attracted much recent attention for their potential in promoting chemical reactions with light. However, the mechanism of LSPR-induced chemical reactions is still not clear. This presentation will discuss the atomic-scale mechanism of plasmonic hot-carrier mediated chemical reaction exampled by H2 dissociation by employing TDDFT calculations and non-adiabatic molecular dynamics. The key observation is that there are nested excited states corresponding to both hot-electron excitation and charge transfer. These nested states cross, which facilitates the transitions depicted in the desorption induced by the electronic transitions model and the surface hopping model. Diabatization of these states shows that the charge transfer states are responsible for H2 dissociation, while the hot electron states do not. Moreover, we found the chemical reaction of molecule is tunable in plasmonic dimer. |
Thursday, March 18, 2021 4:12PM - 4:24PM Live |
V25.00007: Plasmonic-Induced Luminescence of MoSe2 Monolayers in a Scanning Tunneling Microscope (STM) Joel Rigor, Renaud Pechou, Adnen Mlayah, Nicolas Large The use of two-dimensional materials has grown throughout the years as we push to study systems that are in the micro- and nanoscales. When the thickness of these materials is reduced down to a single atomic layer, we can take advantage of the properties of these transition metal dichalcogenides (TMDs) such as the indirect-to-direct band gap transitions in order to induce luminescence from optical fields. Here, we study the luminescence emission from a monolayer of MoSe2 on a gold (Au) substrate using STM. More specifically, we use a theoretical point of view to understand the possibility of plasmon-exciton hybridization within the gap region that may lead to light emission through electrodynamic simulations. We compute near-field intensity spatial distributions using the finite-difference time-domain method (FDTD) to study the coupling mechanism between the MoSe2 monolayer and Au substrate. With our computational model, we observe that there is a significant increase in local-field intensity within the MoSe2 monolayer with respect to the local-field generated in the Au tip- Au surface junction. This significant local-field enhancement in the MoSe2 mediates an effective plasmon-exciton coupling. Computational results are compared and discussed with experimental results. |
Thursday, March 18, 2021 4:24PM - 4:36PM Live |
V25.00008: Farfield-field transmission pattern of a asymetic double sub-wavelength apertures milled on a gold film Abbas Ghaffariesfehani, Kevin Gia Do, somayeh kashani, Robert Riehn We investigate both experimentally and theoretically the far-field diffraction of a set of asymmetric double subwavelength apertures milled on a thin gold film. Asymmetries can arise from a differrence in diameter or a difference in the refractive index between the two apertures. In both cases, the light emerges from the apertures with a relative phase difference, and therefore we anticipate a deflection in the far-field signal. We present a combined experimental and computational study of this system. In particular, we explore the impact of device geometry, presence of refractive index contrast, polarization, and the impact of surface plasmon polariton. We demonstrate that the device is a near-field optical interferometer that provides a far-field monitor for a near-field detection mechanism. |
Thursday, March 18, 2021 4:36PM - 4:48PM On Demand |
V25.00009: Strong Plasmon-Exciton Coupling in Ag-Conjugated Polymer Core-Shell Nanoparticles Christopher Petoukhoff, Keshav M Dani, Deirdre M. O'Carroll Light-matter interactions at the nanoscale is a major prospect of nanophotonics. Tightly-bound Frenkel excitons in organic semiconductors are particularly interesting for coupling with light because of their stability at room-temperature, giving rise to exotic physics such as Bose-Einstein condensation and low-threshold lasing of exciton-polaritons. By exploiting the strong electromagnetic fields confined to the surface of metal nanoparticles, surface plasmons enable strong light-matter coupling within nanoconfined geometries. Thus, strong coupling between surface plasmons and organic excitons can serve as platforms for exploring room-temperature macroscopic quantum phenomena. |
Thursday, March 18, 2021 4:48PM - 5:00PM On Demand |
V25.00010: Noble metal / 2D semiconducting material multilayer structure: a platform to achieve the strong coupling regime Vasileios Karanikolas, Ioannis Thanopulos, Emmanuel Paspalakis The light-matter interaction is important for various practical photonic applications. Multi-level photon sources, quantum emitters (QEs), are used to emit and store light and are important for quantum applications. By smart placement of the QEs close to a nanostructure, their relaxation rate can be accelerated, leading to high Purcell factors. Usually the light-matter interaction is described in the weak coupling regime; at high Purcell factor values, the QE/environment interaction needs to be described in the strong coupling regime. We show that the noble metal /2D semiconducting material (WS2) multilayer structure can be used in order to achieve the strong coupling regime [1]. The noble metal layer supports surface plasmon modes and the WS2 layer hosts excitons with high oscillation strengths. A QE placed in their proximity features an energy splitting in its emission spectrum, a sign of the strong coupling regime. Different noble metal materials (Au, Ag, Cu and Al) are considered; when an Au layer is sandwiched between two WS2 layers, a Rabi-splitting of 257 meV occurs when the transition energy of the QE is 2.02 eV. This effect shows that the light-matter interaction approaches the ultra-strong coupling regime. |
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