Actuellement en préparation ou soumis |
Roslawska, A., Neuman, T., Doppagne, B., Borisov, A. G., Romeo, M., Scheurer, F., Aizpurua, J., & Schull, G. (2021). Mapping Lamb, Stark and Purcell effects at a chromophore-picocavity junction with hyper-resolved fluorescence microscopy. Retrieved April 20, 2024, from https://arxiv.org/abs/2107.01072
Résumé: The interactions between the excited states of a single chromophore with static and dynamic electric fields confined to a plasmonic cavity of picometer dimensions are investigated in a joint experimental and theoretical effort. In this configuration, the spatial extensions of the confined fields are smaller than the one of the molecular exciton, a property that is used to generate fluorescence maps of the chromophores with intra-molecular resolution. Theoretical simulations of the electrostatic and electrodynamic interactions occurring at the chromophore-picocavity junction are able to reproduce and interpret these hyper-resolved fluorescence maps, and reveal the key role played by subtle variations of Purcell, Lamb and Stark effects at the chromophore-picocavity junction.
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Peer-reviewed Publications |
Aguilar-Galindo, F., Borisov, A. G., & Díaz-Tendero, S. (2021). Ultrafast Dynamics of Electronic Resonances in Molecules Adsorbed on Metal Surfaces: A Wave Packet Propagation Approach. J. Chem. Theory Comput., 17(2), 639–654.
Résumé: We present a wave packet propagation-based method to study the electron dynamics in molecular species in the gas phase and adsorbed on metal surfaces. It is a very general method that can be employed to any system where the electron dynamics is dominated by an active electron and the coupling between the discrete and continuum electronic states is of importance. As an example, one can consider resonant molecule–surface electron transfer or molecular photoionization. Our approach is based on a computational strategy allowing incorporating ab initio inputs from quantum chemistry methods, such as density functional theory, Hartree–Fock, and coupled cluster. Thus, the electronic structure of the molecule is fully taken into account. The electron wave function is represented on a three-dimensional grid in spatial coordinates, and its temporal evolution is obtained from the solution of the time-dependent Schrödinger equation. We illustrate our method with an example of the electron dynamics of anionic states localized on organic molecules adsorbed on metal surfaces. In particular, we study resonant charge transfer from the π* orbitals of three vinyl derivatives (acrylamide, acrylonitrile, and acrolein) adsorbed on a Cu(100) surface. Electron transfer between these lowest unoccupied molecular orbitals and the metal surface is extremely fast, leading to a decay of the population of the molecular anion on the femtosecond timescale. We detail how to analyze the time-dependent electronic wave function in order to obtain the relevant information on the system: the energies and lifetimes of the molecule-localized quasistationary states, their resonant wavefunctions, and the population decay channels. In particular, we demonstrate the effect of the electronic structure of the substrate on the energy and momentum distribution of the hot electrons injected into the metal by the decaying molecular resonance.
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Aguilar-Galindo, F., Zapata-Herrera, M., Díaz-Tendero, S., Aizpurua, J., & Borisov, A. G. (2021). Effect of a Dielectric Spacer on Electronic and Electromagnetic Interactions at Play in Molecular Exciton Decay at Surfaces and in Plasmonic Gaps. ACS Photon., 8(12), 3495–3505.
Résumé: The deposition of individual molecules, molecular networks, and molecular layers at surfaces is at the core of surface reactivity, energy harvesting, molecular electronics, and (single) photon sources. Yet, strong adsorbate–substrate interaction on metallic surfaces quenches the excited molecular states and harms many practical applications. Here, we theoretically address the role of a NaCl ionic crystal spacer layer in decoupling an adsorbate from the substrate and therefore changing the interplay between the competing decay channels of an excited molecule driven by electronic and electromagnetic interactions. A quantitative assessment of the corresponding decay rates allows us to establish the minimum thickness of the spacer required for the observation of molecular luminescence from the junction of a scanning tunneling microscope. Our work provides a solid quantitative theoretical basis relevant for several fields of nanotechnology where engineering of ionic crystal spacers allows for adsorbate charge manipulation, reactivity, and photon emission in nanocavities.
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Aguilar-Galindo, F., Borisov, A. G., & Díaz-Tendero, S. (2021). Unveiling the Anisotropic Behavior of Ultrafast Electron Transfer at the Metal/Organic Interface. Appl. Surf. Sci., 554, 149311.
Résumé: Ultrafast electron transfer between adsorbed organic molecules and metal substrates is studied. In particular, the dynamics of the active electron in the nitroethylene anion/metal-copper surface system has been followed in real time using a wave packet propagation approach, allowing an intuitive analysis of the decay of molecule-localized electronic resonances. We find that the strong coupling with the metal substrate leads to an extremely short lifetime (fs) of the molecular resonance. Comparison between the free-electron metal, Cu(100), and Cu(111) surfaces demonstrates that the electronic band structure of the substrate and the shape of the decaying molecular orbital lead to a highly marked anisotropy of the metal continuum states populated by resonant electron transfer from the adsorbate. This finding points at possible anisotropy effects in adsorbate-adsorbate interactions and it is of particular importance in molecular self assembly at metal surfaces, thus opening the way to a rational design of hybrid metal/organic interfaces with tailored electronic properties.
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Aguillon, F., Marinica, D. C., & Borisov, A. G. (2021). Plasmons in Graphene Nanostructures with Point Defects and Impurities. J. Phys. Chem. C, 125(39), 21503–21510.
Résumé: The exceptional electronic and optical properties of graphene are harmed by the unavoidable imperfections of the lattice resulting from mechanical or electronic interaction with the environment. Using a time-dependent approach, we theoretically address the sensitivity of the plasmon modes of graphene nanoflakes to the presence of point vacancy defects and substitutional impurities. We find that the fractions of the defects as low as 10–3 from the total number of carbon atoms in an ideal nanoflake lead to strong broadening of the plasmon resonance in the optical absorption spectrum. In addition to this effect resulting from the elastic and inelastic processes associated with defect-induced scattering and modification of the electronic structure of graphene, we also observe and explain the vacancy and impurity-induced shifts of the plasmon energy. Our work extends the in depth theoretical studies of the optical properties of graphene nanomaterials toward practical situations of nonideal 2D lattices.
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Babaze, A., Esteban, R., Borisov, A. G., & Aizpurua, J. (2021). Electronic Exciton−Plasmon Coupling in a Nanocavity Beyond the Electromagnetic Interaction Picture. Nano Lett., 21(19), 8466–8473.
Résumé: The optical response of a system formed by a quantum emitter and a plasmonic gap nanoantenna is theoretically addressed within the frameworks of classical electrodynamics and the time-dependent density functional theory (TDDFT). A fully quantum many-body description of the electron dynamics within TDDFT allows for analyzing the effect of electronic coupling between the emitter and the nanoantenna, usually ignored in classical descriptions of the optical response. We show that the hybridization between the electronic states of the quantum emitter and those of the metallic nanoparticles strongly modifies the energy, the width, and the very existence of the optical resonances of the coupled system. We thus conclude that the application of a quantum many-body treatment that correctly addresses charge-transfer processes between the emitter and the nanoantenna is crucial to address complex electronic processes involving plasmon–exciton interactions directly impacting optoelectronic applications.
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Bocan, G. A., Breiss, H., Szilasi, S., Momeni, A., Staicu Casagrande, E. M., Sánchez, E. A., Gravielle, M. S., & Khemliche, H. (2021). Dynamical effects as a window into van der Waals interactions in grazing-incidence fast He-atom diffraction from KCl(001). Phys. Rev. B, 104, 235401.
Résumé: In this paper we address, both experimentally and theoretically, the very grazing scattering of He atoms off KCl(001) with incidence along the ⟨100⟩ channel. Our theoretical model combines a semiquantum description of the scattering dynamics and a high-precision interaction potential. By means of a thorough analysis of the quantum phase for in-plane scattering and rainbow trajectories, we are able to connect the presence of the physisorption well with the significant enhancements of the corrugation and rainbow angle, relative to the hard corrugated wall predictions. We trace this connection to dynamical effects on the incident and scattered beams due to their traversing of the physisorption well. Finally, we show that the inclusion of van der Waals interactions in the potential improves the theoretical accord with experiments for both the corrugation and the rainbow angle.
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Wang, Y., Boyer, A. - G., Sauriat-Dorizon, H., Duverger, E., & Riedel, D. (2021). Electronic Structure and Bistable Conformational Study of the Tetraphenylporphyrin Erbium(III) Acetylacetonate Complex on the CaF2/Si(100) Surface at Low Temperatures. J. Phys. Chem. C, 125(26), 14453–14460.
Résumé: The synthesis of tetraphenylporphyrin erbium(III) acetylacetonate (acac) complexes is realized and their properties studied at the nanoscale when adsorbed on a semi-insulating CaF2/Si(100) surface. Our findings reveal that the ErTPP-(acac) molecules can adsorb in two main on-site conformations. Following precisely located dI/dV measurements at various specific positions [phenyls, pyrroles, and Er-(acac)], the relative locations of the Er cation and the apical ligand (acac) can be deciphered for each observed conformation. Hence, one of the adsorbate conformations presents the acac ligand parallel to the porphyrin plane with the Er atom outside the macrocycle plane. The second conformation is related to what is known in the gas phase, where the acac ligand is oriented vertically on top of the Er atom. This work is combined with a theoretical investigation that uses density functional theory methods to bring into light details of the two observed conformations. Additional proofs of our discoveries are related to the vibrational excitations of ErTPP-(acac). A comparison with a theoretical estimation of the vibrational modes reveals how the electronic resonance near the valence-band edge of the insulting layer is suitable to distinguish between the two adsorbed conformations.
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