Peer-reviewed Publications |
Aguillon, F., & Borisov, A. G. (2024). Nonlinear Response of Nanostructured Graphene to Circularly Polarized Light. J. Phys. Chem. C, 128(39), 16576–16587.
Résumé: Using the tight-binding description of graphene and the time-dependent density matrix approach, we theoretically address the nonlinear response of plasmonic graphene nanostructures to the circularly polarized light. The intensity and polarization of emitted harmonics depend on the symmetry of the system and can be analyzed by applying Neumann’s principle. We find that for the nanoflakes comprising thousands of carbon atoms, it is the symmetry of the carbon atom arrangement on the atomic scale that determines the nonlinear response. Therefore, it might be very different from the nonlinear response predicted using the macroscopic geometry. For the compound systems made of several nanoflakes, we reveal the role of the near-field interactions in intensity and circular polarization states of emitted harmonics. Finally, we show that symmetry break by, e.g., lattice defects strongly affects the nonlinear response of graphene nanoflakes to the circularly polarized light. Our work extends the theoretical studies of the nonlinear optical properties of graphene nanomaterials toward spin-carrying light beams.
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Attal, L., Calvo, F., Falvo, C., & Parneix, P. (2024). Coherent state switching using vibrational polaritons in an asymmetric double-well potential. Phys. Chem. Chem. Phys., 2622(9), 753477–754477.
Résumé: The quantum dynamics of vibrational polaritonic states arising from the interaction of a bistable molecule with the quantized mode of a Fabry–Perot microcavity is investigated using a generic asymmetric double-well potential as a simplified one-dimensional model of a reactive molecule. After discussing the role of the light–matter coupling strength in the emergence of avoided crossings between polaritonic states, we investigate the possibility of using these crossings to trigger a dynamical switching of these states from one potential well to the other. Two schemes are proposed to achieve this coherent state switching, either by preparing the molecule in an appropriate vibrational excited state before inserting it into the cavity, or by applying a short laser pulse inside the cavity to obtain a coherent superposition of polaritonic states. The respective influences of dipole moment amplitude and potential asymmetry on the coherent switching process are also discussed.
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Attal, L., Falvo, C., Calvo, F., & Parneix, P. (2024). Modeling the dynamics of quantum systems coupled to large-dimensional baths using effective energy states. J. Chem. Phys., 16011(4), 04410700.
Résumé: The quantum dynamics of a low-dimensional system in contact with a large but finite harmonic bath is theoretically investigated by coarse-graining the bath into a reduced set of effective energy states. In this model, the couplings between the system and the bath are obtained from statistically averaging over the discrete, degenerate effective states. Our model is aimed at intermediate bath sizes in which non-Markovian processes and energy transfer between the bath and the main system are important. The method is applied to a model system of a Morse oscillator coupled to 40 harmonic modes. The results are found to be in excellent agreement with the direct quantum dynamics simulations presented in the work of Bouakline et al. [J. Phys. Chem. A 116, 11118–11127 (2012)], but at a much lower computational cost. Extension to larger baths is discussed in comparison to the time-convolutionless method. We also extend this study to the case of a microcanonical bath with finite initial internal energies. The computational efficiency and convergence properties of the effective bath states model with respect to relevant parameters are also discussed.
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Borisov, A. G. (2024). Model description of electron transfer between PTCDA molecule and metal surface upon molecular adsorption and STM manipulation. Phys. Rev. B, 110, 075413.
Résumé: The coupling between the molecule-localized electronic states and continuum of the electronic states of the metal surface is of paramount importance for adsorption dynamics, surface reactivity, as well as for the electron- and photon-induced processes at metal surfaces. Here, using the model one-active-electron description and wave-packet propagation approach, we study the resonant electron transfer between the perylene-tetracarboxylic-dianhydride (PTCDA) molecule and metal substrate from 0.5 nm separations down to the adsorption distances. We also address the situation where the molecule is lifted up from the substrate using the scanning tunneling microscope. A detailed comparison with the large amount of available experimental data and ab initio calculations allows us to discuss the validity of the method and the main robust effects driving the lifetimes of molecule-localized states that it reveals. Thus we show that the symmetry of molecule-localized states strongly impacts the dependence of the electron transfer rates on the metal band structure and molecule-surface distance. In addition, in full agreement with recent experimental data on scanning tunneling microscopy manipulation where an adsorbed molecule is lifted into the vertical geometry, we find an order of magnitude reduction of the adsorbate-substrate coupling.
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Chahbazian, R., Martin-Drumel, M. - A., & Pirali, O. (2024). High-Resolution Spectroscopic Investigation of the CH2CHO Radical in the Sub-Millimeter Region. The Journal of Physical Chemistry A, 12811(2), 37033–37733.
Résumé: In this work, the pure rotational spectrum of the vinoxy radical (CH2CHO) has been studied at millimeter and sub-millimeter wavelengths (110–860 GHz). CH2CHO was produced by H-abstraction from acetaldehyde (CH3CHO) using atomic fluorine in a double-pass absorption cell at room temperature. A Zeeman-modulation spectrometer, in which an external magnetic field generated inside the absorption cell is amplitude-modulated, was used to record the pure rotational transitions of the radical. The recorded spectra are devoid of signals from closed-shell species, allowing for relatively fast acquisitions over wide spectral windows. Transitions involving values of the rotational quantum numbers N″ and Ka″ up to 41 and 18, respectively, were measured and combined with all available high-resolution literature data (both pure rotation and ground-state combination differences from ro-vibration) to greatly improve the modeling of the CH2CHO spectrum. The combined experimental line list is fit using a semirigid rotor Hamiltonian, and the results are compared to quantum chemical calculations. This laboratory study provides the spectroscopic information needed to search for CH2CHO in various interstellar environments, from cold (e.g., typically 10 K for dense molecular clouds) to warm (e.g., ∼200 K for hot corinos) objects.
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Dupont, J., Hartwig, B., Le Barbu-Debus, K., Lepere, V., Guillot, R., Suhm, M. A., & Zehnacker, A. (2024). Homochiral vs. heterochiral preference in chiral self-recognition of cyclic diols. PCCP, 2622(1411), 1061011–1062111.
Résumé: The structure and clustering propensity of a chiral derivative of cis-1,2-cyclohexanediol, namely, 1-phenyl-cis-1,2-cyclohexanediol (cis-PCD), has been studied under supersonic expansion conditions by combining laser spectroscopy with quantum chemistry calculations. The presence of the phenyl substituent induces conformational locking relative to cis-1,2-cyclohexanediol (cis-CD), and only one conformer of the bare molecule is observed by both Raman and IR-UV double resonance spectroscopy. The homochiral preference inferred for the dimer formation at low enough temperature is in line with the formation of a conglomerate in the solid state. The change in clustering propensity in cis-PCD relative to trans-1,2-cyclohexanediol (trans-CD), which shows heterochiral preference, is explained by the presence of the phenyl substituent rather than the effect of cis-trans isomerism. Indeed the transiently chiral cis-CD also forms preferentially heterodimers, whose structure is very close to that of the corresponding trans-CD dimer.
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Hacquard, A. B., Torres-DIaz, D., Basalgete, R., Toulouse, D., Feraud, G., Del Fre, S., Noble, J. A., Philippe, L., Michaut, X., Fillion, J. - H., Lafosse, A., Amiaud, L., & Bertin, M. (2024). Flux and fluence effects on the vacuum-UV photodesorption and photoprocessing of CO(2) ices. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 26(27), 18741–18752.
Résumé: CO(2) is a major component of the icy mantles surrounding dust grains in planet and star formation regions. Understanding its photodesorption is crucial for explaining gas phase abundances in the coldest environments of the interstellar medium irradiated by vacuum-UV (VUV) photons. Photodesorption yields determined experimentally from CO(2) samples grown at low temperatures (T = 15 K) have been found to be very sensitive to experimental methods and conditions. Several mechanisms have been suggested for explaining the desorption of CO(2), O(2) and CO from CO(2) ices. In the present study, the cross-sections characterizing the dynamics of photodesorption as a function of photon fluence (determined from released molecules in the gas phase) and of ice composition modification (determined in situ in the solid phase) are compared for the first time for different photon flux conditions (from 7.3 x 10(12) photon per s cm(-2) to 2.2x 10(14) photon per s cm(-2)) using monochromatic synchrotron radiation in the VUV range (on the DESIRS beamline at SOLEIL). This approach reveals that CO and O(2) desorptions are decorrelated from that of CO(2). CO and O(2) photodesorption yields depend on photon flux conditions and can be linked to surface chemistry. In contrast, the photodesorption yield of CO(2) is independent of the photon flux conditions and can be linked to bulk ice chemical modification, consistently with indirect desorption induced by an electronic transition (DIET) process.
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Mestdagh, J. - M., Barreau, L., & Poisson, L. (2024). Real-time dynamics of vibronic wavepackets within Rydberg and ion-pair states of molecular iodine. Phys Chem Chem Phys, .
Résumé: Real-time dynamics of vibrationally and electronically excited I_2 molecules has been investigated experimentally using the pump-probe technique. A 2-photon excitation was performed either at 269 nm or 266 nm. An electronic and vibrational wavepacket was built as coherent superposition of a few (269 nm excitation) or many (266 nm excitation) Rydberg states of the and series partly coupled with ion-pair states. The probe operated by ionisation or photodetachement. The energy and angular distribution of the resulting photoelectrons, I(+) photocations and I(-) photoanions were monitored. During the dynamics that is turned on by the pump excitation, the wavepacket splits and explores a variety of electronic states of Rydberg and ion-pair character. The experimental results were complemented by molecular dynamics calculations. This provided invaluable information to identify wavepacket motion along ion-pair potential energy curves.
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Pollak, E., Roncin, P., Allison, W., & Miret-Artes, S. (2024). Grazing incidence fast atom diffraction: general considerations, semiclassical perturbation theory and experimental implications. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 26.
Résumé: Using semiclassical methods, an analytical approach to describe grazing incidence scattering of fast atoms (GIFAD) from surfaces is described. First, we consider a model with a surface corrugated in the scattering plane, which includes the surface normal and the incidence direction. The treatment uses a realistic, Morse potential, within a perturbation approach, and correctly reproduces the basic GIFAD phenomenology, whereby the scattering is directed primarily in the specular direction. Second, we treat the more general case of scattering from a surface corrugated in two-dimensions. Using time averaging along the direction of fast motion in the incidence direction, we derive a time dependent potential for the GIFAD scattering away from a low index direction. The results correctly describe the observation that diffraction is seen only when the scattering plane is aligned close to a low-index direction in the surface plane. For the case of helium scattering from LiF(001) we demonstrate that the resulting theoretical predictions agree well with experiment and show that the analysis provides new information on the scattering time and the length scale of the interaction. The analysis also gives insights into the validity of the axial surface channeling approximation (ASCA) and shows that within first order perturbation theory, along a low-index direction, the full 3-dimensional problem can be represented accurately by an equivalent 2-dimensional problem with a potential averaged along the third dimension. In contrast, away from low-index directions, the effective 2-dimensional potential in the projectile frame is time-dependent.
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Raseev, G. (2024). Optical intensity figures of merit of insulator-metal-insulator and metal-insulator-metal thin-film stacks. Phys. Scr., 99, 085535.
Résumé: Figures of merit (FoM) are used to characterise the mode intensity and leakage of reflection and plane-wave and locally excited transmitted fluxes of simple insulator-metal-insulator (IMI) and metal-insulator-metal (MIM) 2D planar thin-film stacks sustaining a single surface plasmon polariton (SPP) and multiple planar waveguide (PWG) modes. This first comparative study of the intensity FoM (IFoM) of IMI and MIM stack modes is carried out by analysing these observables 3D dispersion graph (observable dispersion/in-plane wave vector/frequency) along 2D cuts where one of the independent variables is fixed. In the spatial domain, the observable 2D dispersion curves along the in-plane wave vector at a given frequency are examined. In the frequency domain, these 2D dispersion curves are examined along the frequency at a given in-plane wave vector. Due to the lower leakage, the quality factors and IFoM of the IMI and MIM thin film stack modes are significantly larger in the spatial domain than in the frequency domain. Our optimized quality factors and IFoMs can be larger than those obtained in some 2D/3D nanoscale samples with an involved geometry.
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Rousseau, P., & Roncin, P. (2024). Fast ion diffraction of protons on NaCl, the discovery of GIFAD. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 554, 165457.
Résumé: Grazing incidence fast atom diffraction (GIFAD or FAD) has become a technique to track the surface topology of crystal surface at the atomic scale. The paper retraces the events that led to the discovery of unexpected quantum behavior of keV atoms during the thesis of Patrick Rousseau in Orsay and Andreas Schueller in Berlin. In Orsay, it started by diffraction spots whereas in Berlin supernumerary rainbows were first identified at keV. Though the discovery was not anticipated, it did not take place by accident, everything was in place several years before, waiting only for an interest in neutral projectiles with a touch of curiosity.
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Woo, S. Y., Shao, F., Arora, A., Schneider, R., Wu, N., Mayne, A. J., Ho, C. - H., Och, M., Mattevi, C., Reserbat-Plantey, A., Moreno, A., Sheinfux, H. H., Watanabe, K., Taniguchi, T., Michaelis de Vasconcellos, S., Koppens, F. H. L., Niu, Z., Stephan, O., Kociak, M., Garcia de Abajo, F. J., Bratschitsch, R., Konecna, A., & Tizei, L. H. G. (2024). Engineering 2D Material Exciton Line Shape with Graphene/h-BN Encapsulation. NANO LETTERS, 24(12), 3678–3685.
Résumé: Control over the optical properties of atomically thin two-dimensional (2D) layers, including those of transition metal dichalcogenides (TMDs), is needed for future optoelectronic applications. Here, the near-field coupling between TMDs and graphene/graphite is used to engineer the exciton line shape and charge state. Fano-like asymmetric spectral features are produced in WS(2), MoSe(2), and WSe(2) van der Waals heterostructures combined with graphene, graphite, or jointly with hexagonal boron nitride (h-BN) as supporting or encapsulating layers. Furthermore, trion emission is suppressed in h-BN encapsulated WSe(2)/graphene with a neutral exciton red shift (44 meV) and binding energy reduction (30 meV). The response of these systems to electron beam and light probes is well-described in terms of 2D optical conductivities of the involved materials. Beyond fundamental insights into the interaction of TMD excitons with structured environments, this study opens an unexplored avenue toward shaping the spectral profile of narrow optical modes for application in nanophotonic devices.
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Zapata-Herrera, M., Rogez, B., Marguet, S., Dujardin, G., Boer-Duchemin, E., & Le Moal, E. (2024). Spectral shifts in tip-induced light from plasmonic nanoparticles in air. Phys. Rev. B, 109(15), 155433.
Résumé: In this article, we carry out an in-depth study of the scanning tunneling microscopy-induced luminescence spectra (STML) of individual plasmonic nanoparticles measured in air. When compared to the results of far-field light scattering measured under the same ambient conditions, the STML measurements show spectral shifts and peak broadening of hundreds of meV, even when a non-plasmonic tip is used for STML. We simulate the near-field excitation and the effect of the tip using the finite-element method and show that these effects alone cannot explain the spectral shifts and peak broadening observed for STML experiments in air. However, the experimental results are well reproduced in the numerical simulations if the screening effect of a water meniscus bridge present in the tip-nanoparticle gap is considered. Our results pave the way for finer interpretations of STML experiments in air, where ignoring this additional screening effect can lead to an incorrect mode assignment of the observed resonances.
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Zhang, W., Zhang, X., Ono, L. K., Qi, Y., & Oughaddou, H. (2024). Recent Advances in Phosphorene: Structure, Synthesis, and Properties. SMALL, 20, 2303115.
Résumé: Phosphorene is a 2D phosphorus atomic layer arranged in a honeycomb lattice like graphene but with a buckled structure. Since its exfoliation from black phosphorus in 2014, phosphorene has attracted tremendous research interest both in terms of synthesis and fundamental research, as well as in potential applications. Recently, significant attention in phosphorene is motivated not only by research on its fundamental physical properties as a novel 2D semiconductor material, such as tunable bandgap, strong in-plane anisotropy, and high carrier mobility, but also by the study of its wide range of potential applications, such as electronic, optoelectronic, and spintronic devices, energy conversion and storage devices. However, a lot of avenues remain to be explored including the fundamental properties of phosphorene and its device applications. This review recalls the current state of the art of phosphorene and its derivatives, touching upon topics on structure, synthesis, characterization, properties, stability, and applications. The current needs and future opportunities for phosphorene are also discussed.
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