Peer-reviewed Publications |
Aguillon, F., Marinica, D. C., & Borisov, A. G. (2022). Atomic-scale control of plasmon modes in graphene nanoribbons. Phys. Rev. B, 105, L081401.
Résumé: We address the possibility of atomic-scale control of the plasmon modes of graphene nanostructures. Using the time-dependent many-body approach we show that for the zigzag and armchair nanoribbons, the single carbon atom vacancy results in “on” and “off” switching of the longitudinal plasmon modes or in a change of their frequency. The effect stems from the robust underlying physical mechanism based on the strong scattering of the two-dimensional (2D) electrons on the vacancy defects in graphene lattice. Thus our findings establish a platform for optical response engineering or sensing in 2D materials.
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Babaze, A., Ogando, E., Stamatopoulou, P. E., Tserkezis, C., Mortensen, N. A., Aizpurua, J., Borisov, A. G., & Esteban, R. (2022). Quantum surface effects in the electromagnetic coupling between a quantum emitter and a plasmonic nanoantenna: time-dependent density functional theory vs. semiclassical Feibelman approach. Opt. Express, 30(12), 21159–21183.
Résumé: We use time-dependent density functional theory (TDDFT) within the jellium model to study the impact of quantum-mechanical effects on the self-interaction Green’s function that governs the electromagnetic interaction between quantum emitters and plasmonic metallic nanoantennas. A semiclassical model based on the Feibelman parameters, which incorporates quantum surface-response corrections into an otherwise classical description, confirms surface-enabled Landau damping and the spill out of the induced charges as the dominant quantum mechanisms strongly affecting the nanoantenna–emitter interaction. These quantum effects produce a redshift and broadening of plasmonic resonances not present in classical theories that consider a local dielectric response of the metals. We show that the Feibelman approach correctly reproduces the nonlocal surface response obtained by full quantum TDDFT calculations for most nanoantenna–emitter configurations. However, when the emitter is located in very close proximity to the nanoantenna surface, we show that the standard Feibelman approach fails, requiring an implementation that explicitly accounts for the nonlocality of the surface response in the direction parallel to the surface. Our study thus provides a fundamental description of the electromagnetic coupling between plasmonic nanoantennas and quantum emitters at the nanoscale.
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Koval, N. E., Sánchez-Portal, D., Borisov, A. G., & Díez Muiño, R. (2022). Time-dependent density functional theory calculations of electronic friction in non-homogeneous media. Phys. Chem. Chem. Phys., 24(34), 20239–20248.
Résumé: The excitation of low-energy electron–hole pairs is one of the most relevant processes in the gas–surface interaction. An efficient tool to account for these excitations in simulations of atomic and molecular dynamics at surfaces is the so-called local density friction approximation (LDFA). The LDFA is based on a strong approximation that simplifies the dynamics of the electronic system: a local friction coefficient is defined using the value of the electronic density for the unperturbed system at each point of the dynamics. In this work, we apply real-time time-dependent density functional theory to the problem of the electronic friction of a negative point charge colliding with spherical jellium metal clusters. Our non-adiabatic, parameter-free results provide a benchmark for the widely used LDFA approximation and allow the discussion of various processes relevant to the electronic response of the system in the presence of the projectile.
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Peña Román, R. J., Bretel, R., Pommier, D., Parra López, L. E., Lorchat, E., Boer-Duchemin, E., Dujardin, G., Borisov, A. G., Zagonel, L. F., Schull, G., Berciaud, S., & Le Moal, E. (2022). Tip-Induced and Electrical Control of the Photoluminescence Yield of Monolayer WS2. Nano Lett., 22(23), 9244–9251.
Résumé: The photoluminescence (PL) of monolayer tungsten disulfide (WS2) is locally and electrically controlled using the nonplasmonic tip and tunneling current of a scanning tunneling microscope (STM). The spatial and spectral distribution of the emitted light is determined using an optical microscope. When the STM tip is engaged, short-range PL quenching due to near-field electromagnetic effects is present, independent of the sign and value of the bias voltage applied to the tip–sample tunneling junction. In addition, a bias-voltage-dependent long-range PL quenching is measured when the sample is positively biased. We explain these observations by considering the native n-doping of monolayer WS2 and the charge carrier density gradients induced by electron tunneling in micrometer-scale areas around the tip position. The combination of wide-field PL microscopy and charge carrier injection using an STM opens up new ways to explore the interplay between excitons and charge carriers in two-dimensional semiconductors.
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Peña Román, R. J., Pommier, D., Bretel, R., Parra López, L. E., Lorchat, E., Chaste, J., Ouerghi, A., Le Moal, S., Boer-Duchemin, E., Dujardin, G., Borisov, A. G., Zagonel, L. F., Schull, G., Berciaud, S., & Le Moal, E. (2022). Electroluminescence of monolayer WS2 in a scanning tunneling microscope: Effect of bias polarity on spectral and angular distribution of emitted light. Phys. Rev. B, 106, 085419.
Résumé: Inelastic electron tunneling in a scanning tunneling microscope is used to generate excitons in monolayer tungsten disulfide (WS2). Excitonic electroluminescence is measured both at positive and negative sample bias. Using optical spectroscopy and Fourier-space optical microscopy, we show that the bias polarity of the tunnel junction determines the spectral and angular distribution of the emitted light. At positive sample bias, only emission from excitonic species featuring an in-plane transition dipole moment is detected. Based on the spectral distribution of the emitted light, we infer that the dominant contribution is from charged excitons, i.e., trions. At negative sample bias, additional contributions from lower-energy excitonic species are evidenced in the emission spectra and the angular distribution of the emitted light reveals a mixed character of in-plane and out-of-plane transition dipole moments.
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Rosławska, A., Neuman, T., Doppagne, B., Borisov, A. G., Romeo, M., Scheurer, F., Aizpurua, J., & Schull, G. (2022). Mapping Lamb, Stark, and Purcell Effects at a Chromophore-Picocavity Junction with Hyper-Resolved Fluorescence Microscopy. Phys. Rev. X, 12, 011012.
Résumé: The interactions of the excited states of a single chromophore with static and dynamic electric fields spatially varying at the atomic scale are investigated in a joint experimental and theoretical effort. In this configuration, the spatial extension of the fields confined at the apex of a scanning tunneling microscope tip is smaller than that of the molecular exciton, a property used to generate fluorescence maps of the chromophore with intramolecular resolution. Theoretical simulations of the electrostatic and electrodynamic interactions occurring at the picocavity junction formed by the chromophore, the tip, and the substrate reveal the key role played by subtle variations of Purcell, Lamb, and Stark effects. They also demonstrate that hyper-resolved fluorescence maps of the line shift and linewidth of the excitonic emission can be understood as images of the static charge redistribution upon electronic excitation of the molecule and as the distribution of the dynamical charge oscillation associated with the molecular exciton, respectively.
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Thébault, P., Ammoun, M., Boudjemaa, R., Ouvrard, A., Steenkeste, K., Bourguignon, B., & Fontaine-Aupart, M. - P. (2022). Surface functionalization strategy to enhance the antibacterial effect of nisin Z peptide. Surf. Interfaces, 30, 101822.
Résumé: One of the main challenges when building antibacterial surfaces with antimicrobial peptides (AMPs) is to preserve their antimicrobial activity after stable immobilization of the peptides. Among all parameters, order/conformation of self-assembled monolayers, used as spacer, is one the most important. Herein we report the covalent immobilization of the nisin Z peptide on a gold surface functionalized with a self-assembled monolayer of 11-mercaptoundecanoic acid (MUA) alone or mixed with 6-mercaptohexanol, used as a spacer. The MUA acid is activated by treatment with carbodiimide/N-hydroxysuccinimidine and then reacts with nisin Z to form amide bonds via the N terminal part of the peptide. We have characterized each step of the surface modification using X-ray photoelectron spectroscopy, FTIR-ATR spectroscopy and contact angle measurements. The combined results show the success of each functionalization step. Additionally, SFG brings information on the orientation and conformational ordering of the self-assembled monolayers. Indeed, a better order of MUA25 layers compared to MUA was observed due to the spacing of carboxylic acid groups. The antibacterial activity of the immobilized AMPs against Staphylococcus aureus is evaluated using confocal microscopy and bacterial counting: it increases with a better order of the SAMs rather than a greater peptide concentration. This study provides fundamental insights on how to engineer AMPs and substrate to produce efficient biocidal surfaces.
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