Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session S02: Plasmonics and ExcitonicsRecordings Available
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Chair: Saif Ullah, Wake Forest University Room: McCormick Place W-175C |
Thursday, March 17, 2022 8:00AM - 8:12AM |
S02.00001: Generation of Hot Electrons in Plasmonic Nanoparticles with Complex Shapes Eva Yazmin Santiago Santos, Alexander O Govorov, Lucas V Besteiro The generation of hot electrons in plasmonic nanoparticles is an intrinsic response to light, which strongly depends on the nanoparticle's shape and composition, as well as on the excitation wavelength. In this study, we present a formalism that describes the generation of these hot electrons for gold nanospheres, nanorods, and nanostars. The rate of the hot electron generation is computed for all of them, and the role of the shape is analyzed. Among them, the nanostars are the most efficient at generating hot electrons, with an internal energy efficiency of approximately 25%, owing to multiple factors such as hot spots, for example. The physical principles analyzed in this study can be used for applications in photocatalysis and photodetection. |
Thursday, March 17, 2022 8:12AM - 8:24AM |
S02.00002: Dynamic Analysis of Hot Carrier Driven Photocatalysis on Plasmonic Grating and Nanoantenna Photoelectrodes Yu Wang, Yi Wang, Indu Aravind, Zhi Cai, Lang Shen, Boxin Zhang, Bo Wang, Jihan Chen, Bofan Zhao, Haotian Shi, Jahan M Dawlaty, Stephen B Cronin We studied the hot carrier-driven photocatalysis on plasmonic gratings as well as nanoantenna photoelectrodes, mainly focusing on water splitting reactions. By varying the incident angles of p-polarized light (electric field is perpendicular to the grating lines), sharp troughs are observed in the reflectance spectra, which is originated from surface plasmon polaritons(SPPs). Photocurrent measured on Ag continuous film gratings is 44 times higher when light is p-polarized compared to s-polarized under 785 nm laser incidence under the bias of -0.5 V vs Ag/AgCl reference electrode. We also investigated the ultrafast dynamics of hot electron injection from Au nanoantenna photoelectrodes to water adsorbates by exciting localized surface plasmon resonance (LSPR). In situ ultrafast pump-probe transient absorption (TA) measurements are used to measure the hot electron injection dynamics, which shows a depletion peak is observed around the resonant wavelength. Finite Difference Time Domain (FDTD) simulations are carried out to study the electric field distribution near the surface of those photoelectrodes under resonant conditions, revealing various hot spots and different resonant modes. |
Thursday, March 17, 2022 8:24AM - 8:36AM |
S02.00003: Quantifying plasmonic hot carrier charge transfer in photoelectrochemical systems Aaron H Rose, Jao van de Lagemaat We measure the IQE of plasmon-derived hot carrier charge transfer to drive chemical reactions at a plasmonic gold working electrode in aqueous electrolyte. At positive applied potential, we oxidize ascorbic acid through transfer of hot holes and at negative applied potential, electron transfer drives the hydrogen evolution reaction (HER). |
Thursday, March 17, 2022 8:36AM - 8:48AM |
S02.00004: Plasmonic Chiral Photoheating using DNA-Nanocrystal Assemblies Oscar R Avalos-Ovando, Lucas V Besteiro, Alexander O Govorov Over the past decade, the field of chiral plasmonics has emerged as a novel way of manipulating the optical properties of metallic nanocrystals (NCs). Specifically, it was found that plasmonic NCs generate heat efficiently in the presence of electromagnetic radiation and even strongly when this is at the frequency of the plasmon resonance, hence allowing a great deal of tunability. Here, we use a chiral DNA-assembled nanorod pair as a model system for chiral plasmonic photo-heating, and we study the subsequent chiral photo-melting of its components. We show that both the enantiomeric excess and consequent circular dichroism can be controlled with chiral light, for both the single-complex and the collective heating regimes. The chiral asymmetry factors of the calculated photothermal and photo-melting effects exceed the values typical for the chiral molecular photochemistry at least 10-fold. Our proposed mechanism can be used to develop chiral photo-responsive systems controllable with circularly polarized light, e.g. for uses in photo-medicine or photocatalysis. |
Thursday, March 17, 2022 8:48AM - 9:00AM |
S02.00005: Plasmon-phonon-intersubband transition interactions at THz frequency in Bi2Se3-GaAs heterostructures Quang To, Zhengtianye Wang, Dai Q Ho, Ruiqi Hu, Wilder Acuna Gonzalez, Yongchen Liu, Garnett W Bryant, Anderson Janotti, Joshua Zide, Stephanie Law, Matthew F Doty In this work we probe theoretically strong coupling at THz frequency in a system consisting of Bi2Se3 and AlGaAs/GaAs quantum wells, focusing on the creation of new hybrid excitation modes, namely Dirac plasmon phonon intersubband transition (ISBT) polaritons. Rabi splitting arising from the interactions among the THz excitations in the system shows features of strong coupling which can be experimentally observable. Our calculations based on scattering matrix method reveal that the Rabi splitting depends strongly on doping level and scattering rate in the quantum wells, as well as on the thickness of the GaAs spacer layer which separates the quantum well structures from the topological insulator (TI) layer. Our model also addresses contributions from an extra two-dimensional electron gas (2DEG) occurring at the Bi2Se3/GaAs interface as predicted by density functional theory calculations. This massive two-dimensional electron gas gives rise to a shift in the dispersion of the Dirac plasmon-ISBT polaritons to higher frequencies. This work lays the foundation and serves as a guide for setting up future experimental explorations into the coupling between a TI and a III-V heterostructure. |
Thursday, March 17, 2022 9:00AM - 9:12AM |
S02.00006: Ultrafast Relaxation Dynamics in Bimetallic Plasmonic Nanoparticles Sanchari Chowdhury, Philip Mantos, Sangwan Sim, Rohit P. Prasankumar, Alyssa Bierlie, Steven McCrory Combining a plasmonic metal, such as gold, with other popular catalysts, such as Ni or Pt, can extend its benefit to many energy-extensive reactions catalyzed by those metals. The efficiency of a plasmon-enhanced catalytic reaction is mainly determined by the light absorption cross-section and the photoexcited charge carrier relaxation dynamics of the nanoparticles. We have investigated the charge carrier relaxation dynamics of gold/nickel (Au/Ni) and gold/platinum (Au/Pt) bimetallic nanoparticles. We found that the addition of Ni or Pt to gold can reduce light absorption in gold nanoparticles. However, electron-phonon coupling rates in Au/Ni and Au/Pt nanoparticles are significantly faster than that of pure Au nanoparticles. This is due to the fact that both Ni and Pt possess significantly larger electron-phonon coupling constants and higher densities of states near the Fermi level in comparison to Au. Additionally, the phonon-phonon coupling rate of bimetallic Au/Pt and Au/Ni nanoparticles was significantly different than that of pure gold nanoparticles, due to the acoustic impedance mismatch at the nanoparticle/substrate interface. Our findings provide important insights towards the rational design of bimetallic plasmonic catalysts. |
Thursday, March 17, 2022 9:12AM - 9:24AM |
S02.00007: Crossover from above-threshold to below-threshold plasmonic electroluminescent emission at the atomic scale Yunxuan Zhu, Longji Cui, Mahdiyeh Abbasi, Douglas Natelson Light emission from biased metal tunnel junctions has been known for decades, with renewed research interest brought by the rise of the field of plasmonics. Controversies have existed regarding different possible underlying mechanisms that represent distinct physical processes in generating far field emission. Whether the photons come from inelastic processes involving the coherent tunneling of discrete electrons or from radiative recombination of plasmonically excited hot carriers still remains elusive. Here, leveraging planar, lithographically defined aluminum tunnel junctions, we report a crossover from above-threshold emission to below-threshold emission when enlarging the tunneling gap distance via electromigration. Analysis of spectra shows that different above-threshold mechanisms under hot debate can coexist during the light emission process, and particular mechanisms are respectively dominant at different conductance ranges. These experiments show that the light emission mechanism in metal tunnel junctions is really a question of current and voltage regimes and relative timescales. |
Thursday, March 17, 2022 9:24AM - 9:36AM |
S02.00008: Observation of a rich diversity of exciton-polaritons in Ag-CNTs bilayers James C Howard, Bryon W Larson, Mark D Steger, Jeffrey L Blackburn, Andrew J Ferguson, Aaron H Rose We demonstrate strong coupling between s- and p-polarized polaritons and the S22 transition in (6,5) carbon nanotubes (CNTs) as well as p-polarized polaritons and the S11 transition, in Ag-CNT thin film bilayers. Employing angle-resolved photoreflectance in the Kretschmann-Raether (K-R) configuration, we first show strong coupling between the p-polarized surface plasmon mode and the ground state S11 exciton. We find Rabi splitting of ~100 meV which is ~8% of the S11 exciton energy (1.24 eV), approaching the ultrastrong coupling limit. By varying the thickness of the CNT layer, we are able to observe higher energy polariton modes in both polarizations that couple to the S22 transition. |
Thursday, March 17, 2022 9:36AM - 9:48AM |
S02.00009: Steering dark state formation in molecular aggregates with DNA scaffolds: The interplay between Coulombic and charge transfer interactions Maria A Castellanos, Stephanie M Hart, James L Banal, Adam P Willard DNA-scaffolded dye aggregates have emerged as a promising platform for designing tractable model systems to understand the function of delocalized excitons in light harvesting, as the DNA provides a diverse molecular toolbox to control the spatial relationships of the dyes. However, in tightly packed aggregates Charge Transfer (CT) interactions can arise through spatial overlap of molecular orbitals between monomers and can destructively interfere with long-range Coulombic interactions, leading to significant quenching of measured fluorescence. Here we investigated the interference between short-range CT and long-range Coulombic interactions by studying indolenine squaraine dimers scaffolded on duplex DNA. Molecular dynamics and quantum mechanical simulations were performed on different squaraine-DNA arrangements to reveal the underlying molecular mechanisms on how this interplay is affected by the scaffolding. Paired with time-resolved fluorescence and transient absorption spectroscopy experiments, our results demonstrate how DNA scaffolds can influence the excited-state decay pathways of molecular dimers, which is critical for designing molecular aggregates for light-harvesting and computing applications. |
Thursday, March 17, 2022 9:48AM - 10:00AM |
S02.00010: Disorder enhanced energy transfer with the assistance of cavity QED Weijun Wu, Bo Fu, Andrew E Sifain, Gregory D Scholes Energy transfer is a ubiquitous phenomenon in nature to describe the dynamics in photosynthetic complexes, molecular aggregates, and donor-acceptor systems. One detrimental factor for energy transfer efficiency is disorder, originating from inherent system properties. Here we theoretically report a new way to eliminate the negative impact of disorder in an excitonic system by strongly coupling it to a photonic cavity mode, where the cavity photon bridges spatially separated sites and builds an additional energy transport channel. Our analysis of the open quantum system shows that there are three different regimes of energy transfer characterized by the degree of disorder, molecular hopping, and Rabi splitting. Namely, with the assistance of the cavity, disorder in certain regimes can actually enhance energy transfer in the dissipating system and can even have a higher transfer efficiency than the pristine system. These results provide insight into the design of next-generation energy transfer materials leveraging hybrid light-matter states. |
Thursday, March 17, 2022 10:00AM - 10:12AM |
S02.00011: Asymmetric generation and detection of surface plasmons polaritons using near-field aperture probes Juan M Merlo-Ramirez In recent years, the generation and detection of surface plasmons polaritons (SPPs) using near-field microscopy probes has become one of the most important research areas. Actually, nowadays most of the light-matter interactions studies rely on this technique. Though, few works have been reported to the date regarding the asymmetric generation of SPPs on metallic surfaces. Moreover, the asymmetric generation of SPPs is attributed exclusively to scattering near-field probes. With this in mind, this work is dedicated to demonstrate that the asymmetric generation of SPPs is not exclusive of such probes. In fact, it is shown that near-field aperture probes in collection mode can also generate and detect such a phenomenon. In addition, by analyzing the momentum components of the near-field images, it was demonstrated that the observed interactions are the result of the interference between SPPs of different momenta, confirming existing reports. |
Thursday, March 17, 2022 10:12AM - 10:24AM |
S02.00012: Ultrafast carrier dynamics in Cu9S5 flakes Andrea Villa, Madina Telkhozhayeva, Fabio Marangi, Eti Teblum, Aaron M Ross, Mirko Prato, Luca Andena, Roberto Frassine, Francesco Scotognella, Gilbert Nessim Copper chalcogenides have attracted attention due to their intrinsic doping properties. These materials display high carrier concentrations due to their defect-heavy structures, thus by varying their stoichiometry tunable plasmonic resonances can be observed, as it was shown previously for Cu2-xS/Se/Te, with 09S5 were studied by means of ultrafast transient absorption (TA) spectroscopy. The samples were pumped at 50 kHz with 50 fs pulses centered a 1.65 μm, in the region of the near-infrared (NIR) plasmonic resonance, and probed in the 1.1-1.6 μm range. The measurement was performed with a high sensitivity TA spectrometer utilizing a birefringent delay line interferometer and lock-in detection, avoiding the need for expensive IR multi-pixel detectors. We were able to measure the relaxation dynamics of the excited electrons, which are dominated by a fast decay (τ1~400 fs) associated to electron-phonon scattering followed by a long-lived bleaching (τ2>>50 ps) due to trapping of electrons in defect states. We confirm the plasmonic nature of Cu9S5, which is promising for incorporation into hot-electron-harvesting solar cells. |
Thursday, March 17, 2022 10:24AM - 10:36AM |
S02.00013: Bacteria-induced changes in the ultrafast plasmonic response of silver nanostructured surfaces Aaron M Ross, Giuseppe M Paterno, Silvia Pietralunga, Simone Normani, Nicholas Dalla Vedova, Jakkarin Limwongyut, Gaia Bondelli, Liliana Moscardi, Guillermo C Bazan, Francesco Scotognella, Guglielmo Lanzani The antimicrobial properties of silver have been known for millenia, finding use in coinage, cutlery, medical device coatings, and textiles. The consensus regarding the origin of this mechanism is that bacterial metabolism is disrupted by uptake of silver ions following oxidative dissolution at the bacteria-silver interface. The manifestation of this interaction on the plasmonic response of silver nanoparticles is investigated here. Changes in the nanoparticle crystallinity, size, and shape are observed after interaction with E.coli via transient absorption spectroscopy. Bacterial exposure leads to a decrease in the electron-phonon coupling time, an increase in the lattice-environment coupling time, and rapid damping of coherent oscillations. This bacterial action was studied using E.coli, known to be susceptible to silver ion uptake, and was enhanced with a membrane permeability-increasing agent. The changes in the plasmonic response are explained by an increase in the free electron density and amorphization of the silver nanoparticles, as well as modification of the silver nanocrystal film thickness. |
Thursday, March 17, 2022 10:36AM - 10:48AM |
S02.00014: Strong coupling regime and quantum material response Vasileios Karanikolas, Ioannis Thanopulos, Joel Cox, Takashi Takashi Kuroda, Jun-ichi Inoue, N. A Mortensen, Emmanuel Paspalakis, Christos Tserkezis The functionality of localized quantum emitters (QEs) is limited by their slow operation; making them susceptible to dephasing and decoherence effects through the interaction of the sourses with their environment. Plasmons in metal nanostructures (NSs) are used to accelarate the relaxation of the QEs. When the QE/NS separation distance is small their interaction can be within the strong coupling regime, where coherent energy exchange is observed between QE and NS. While the nonclassical behavior of such quantum emitters (QEs) is well-understood in this context, the role of quantum and surface effects in the plasmonic NS is usually neglected. The relaxation dynamics of a two-level QE placed nearby metal-dielectric layered NSs is investigated, combining the Green's tensor approach with the Feibelman $d$-parameter formalism to theoretically explore the influence of quantum surface effects in the metal. Having identified electron spill-out as the dominant source of quantum effects in jellium-like metals, we focus our study on sodium. The results presented reveal a clear splitting in the emission spectrum, indicative of having reached the strong-coupling regime, and non-Markovian relaxation dynamics of the emitter. Our findings establish that strong light--matter coupling is not suppressed by the emergence of nonclassical surface effects in the optical response of the metal. |
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