Publications

2023

• Plasmonics in ultra relativistic regime
  
  • Kleij Paula
  , 2023. The proliferation of short-pulse multi-Petawatt laser facilities around the world motivates the exploration of increasingly higher field regimes and more important particle acceleration as experiments with intensities exceeding 10^24 W/cm^2 will soon become available. In this new era of ultra-intense relativistic laser-plasma interaction physics, the extension of the study of plasmonics towards higher intensity regimes, where nonlinear and relativistic effects progressively come into play, is of fundamental interest for the physics of relativistic plasmas. Previous experiments have shown that the resonant excitation of surface plasma waves (SPW) by ultra-high intensity fs lasers impinging on a solid-density structured target strongly enhances the laser-plasma coupling and can efficiently accelerate electrons. When extending the regime of ultra-high laser intensity interaction beyond 10^21 W/cm2, we might obtain SPW with extremely large amplitudes at the over-dense plasma surface, potentially allowing to obtain unprecedentedly high currents of energetic electrons. The aim of the present PhD work is to explore theoretically and numerically, through Particle-in-Cell simulations performed with SMILEI, the generation of these fast electron beams in relativistic laser-solid interaction by using properly-structured targets whose surface characteristics allow SPW excitation or local electromagnetic modes in increasingly relativistic laser regimes. In this work we propose a novel set-up which permits to tune SPW duration and intensity and consequently the electron bunch characteristics. Indeed, by impinging a laser with wavefront rotation (WFR) on a smart grating design, we both shorten the duration (down to very few optical cycles) and increase the intensity of SPW, thus favoring the production of ultra-short, energetic electron bunches. In the laser-plasma relativistic regime of interaction (10^21 W/cm2), we show that such SPW are found to accelerate high-charge (few 10’s of pC), high-energy (up to 70 MeV), and ultra-short (few fs) electron bunches. Extending the research to the ultra-relativistic regime (> 10^21 W/cm2), we have identified the key parameters to ensure the excitation and survival of these surface plasma waves. The produced electron bunches experience strong acceleration, therefore emitting large amounts of electromagnetic radiation with interesting characteristics such as directionality, brightness, spectral range etc. Furthermore, when comparing the photon emission in different set-up geometries, we notice that the set-up favouring SPW excitation also emit photons with higher energies with respect to the case favouring direct laser vacuum acceleration. This proves that SPW may generate innovative ways to manipulate and amplify high power laser light pulses, paving the way to ground-breaking ultra-short synchronized light and electron sources which could find applications in the exploration of ultra-fast electronic processes, free electron laser or the production of XUV rays. In addition, we propose the implementation of a diagnostic, based on the Lienard Wiechert potentials, complementing the pre-existing radiation modules in SMILEI. The implementation of this radiation is not only interesting for the study of SPW excitation and electron acceleration in the ultra-relativistic regime, but also for the investigation of betatron radiation and high harmonic generation among many others.
• Robustness of electronic screening effects in electron spectroscopies: Example of V$_2$O$_5$
  
  • Gorelov Vitaly
  • Reining Lucia
  • Lambrecht Walter R. L.
  • Gatti Matteo
  Physical Review B, American Physical Society, 2023, 107 (7), pp.075101. In bulk and low-dimensional extended systems, the screening of excitations by the electron cloud is a key feature governing spectroscopic properties. Widely used computational approaches, especially in the framework of many-body perturbation theory, such as the GW approximation and the resulting approximate Bethe-Salpeter equation, are explicitly formulated in terms of the screened Coulomb interaction. In the present work we explore the effect of screening in absorption and electron energy loss spectroscopy, concentrating on the effect of local distortions on the screening and elucidating the resulting changes in the various spectra. Using the layered bulk oxide V2O5 as prototype material, we show in which way local distortions affect the screening, and in which way changes in the screening impact electron energy loss and absorption spectra including excitons. We highlight cancellations that make many-body effects in the spectra very robust with respect to structural modifications, while the band structure undergoes significant changes and the nature of the excitations may also be affected. This yields insight concerning the structure-properties relations that are crucial for the use of V2O5 as energy storage material, and more generally, that may be used to optimize the analysis and the calculation of electronic spectra in complex materials. (10.1103/PhysRevB.107.075101)
  DOI : 10.1103/PhysRevB.107.075101
• Investigation of Planckian behavior in a high-conductivity oxide: PdCrO$_2$
  
  • Zhakina Elina
  • Daou Ramzy
  • Maignan Antoine
  • Mcguinness Philippa
  • König Markus
  • Rosner Helge
  • Kim Seo-Jin
  • Khim Seunghyun
  • Grasset Romain
  • Konczykowski Marcin
  • Tulipman Evyatar
  • Mendez-Valderrama Juan Felipe
  • Chowdhury Debanjan
  • Berg Erez
  • Mackenzie Andrew
  Proceedings of the National Academy of Sciences of the United States of America, National Academy of Sciences, 2023, 120 (36), pp.e2307334120. The layered delafossite metal PdCrO$_2$ is a natural heterostructure of highly conductive Pd layers Kondo coupled to localized spins in the adjacent Mott insulating CrO$_2$layers. At high temperatures $T$ it has a $T$-linear resistivity which is not seen in the isostructural but non-magnetic PdCoO$_2$. The strength of the Kondo coupling is known, as-grown crystals are extremely high purity and the Fermi surface is both very simple and experimentally known. It is therefore an ideal material platform in which to investigate 'Planckian metal' physics. We do this by means of controlled introduction of point disorder, measurement of the thermal conductivity and Lorenz ratio and studying the sources of its high temperature entropy. The T-linear resistivity is seen to be due mainly to elastic scattering and to arise from a sum of several scattering mechanisms. Remarkably, this sum leads to a scattering rate within 10% of the Planckian value of k $_BT/$$\hbar$ . (10.1073/pnas.2307334120)
  DOI : 10.1073/pnas.2307334120
• Visualizing screening in noble-metal clusters: static vs. dynamic
  
  • Sinha-Roy Rajarshi
  • García-González Pablo
  • López-Lozano Xóchitl
  • Weissker Hans-Christian
  Physical Chemistry Chemical Physics, Royal Society of Chemistry, 2023, 25 (3), pp.2075-2083. The localized surface-plasmon resonance of metal nanoparticles and clusters corresponds to a collective charge oscillation of the quasi-free metal electrons. The polarization of the more localized d electrons opposes the overall polarization of the electron cloud and thus screens the surface plasmon. By contrast, a static electric external field is well screened, as even very small noble-metal clusters are highly metallic: the field inside is practically zero except for the effect of the Friedel-oscillation-like modulations which lead to small values of the polarization of the d electrons. In the present article, we present and compare representations of the induced densities (i) connected to the surface-plasmon resonance and (ii) resulting from an external static electric field. The two cases allow for an intuitive understanding of the differences between the dynamic and the static screening. (10.1039/D2CP04316E)
  DOI : 10.1039/D2CP04316E
• Plasmonic Properties of SrVO Bulk and Nanostructures
  
  • Su Chia‐ping
  • Ruotsalainen Kari
  • Nicolaou Alessandro
  • Gatti Matteo
  • Gloter Alexandre
  Advanced Optical Materials, Wiley, 2023, 11. Correlated metals, such as SrVO3 (SVO) or SrNbO3, are promising materials for optical devices such as transparent conductors. Here, a real-space and reciprocal-space electron-energy-loss-spectroscopy (EELS) investigation of SVO bulk and nanostructures is reported. An intense 1.35 eV excitation with a weak energy dispersion is observed in the loss function and is attributed to a bulk plasmonic excitation from the 3d-t2g orbitals. Ab initio calculations done within a time-dependent density functional theory framework reveal that a 1.5 band renormalization is sufficient to reproduce quantitatively this d–d plasmon energy and dispersion. The corresponding localized surface plasmon (LSP) peaks are measured by EELS on various nanostructures and are compared to finite-difference time-domain simulations. These LSPs exhibit quality factors above canonical materials (e.g., indium tin oxide) in the near-infrared regime, demonstrating that SVO is also a material of high interest for plasmonic applications. Finally, by phasing out the surface plasmon contribution with EELS collected at minute off-dipolar conditions, the bulk-type plasmonic values are retrieved with nanometrical resolution. Core–shelled electronic structures are then observed for nanorods designed by focused ion beam (FIB), revealing a bandgap opening due to FIB damage. It is envisioned that similar bulk measurement can be feasible for most of the transition metal oxide nanostructures. (10.1002/adom.202202415)
  DOI : 10.1002/adom.202202415
• Silver photochemical reactivity under electronic irradiation of zinc-phosphate and sodium gallo-phosphate glasses
  
  • Alassani Fouad
  • Desmoulin Jean Charles
  • Cavani Olivier
  • Petit Yannick
  • Cardinal Thierry
  • Ollier Nadège
  Journal of Non-Crystalline Solids, Elsevier, 2023, 600, pp.122009 (10 p.). In the present work, the effect of electron irradiations on silver-containing phosphate glasses using a 2.5 MeV electron beam has been explored by Electron Spin Resonance (ESR) and luminescence spectroscopy. The process involved in the interaction of electron beam with both the silver-containing and silver-free phosphate glass matrix and the formation of colored centers is discussed. This allowed an understanding of the initial phenomena of electron deposition and charge trapping that supports the photosensitivity of these glasses by identifying the point defects and the Ag species. The effect of the silver concentration and the structure of the glass depending on the integrated dose have been investigated. The insitu cathodoluminescence measurements give additional valuable information about the cascade of chemical reactions in the formation of new silver species, namely from the initial silver ions to the molecular silver clusters. (10.1016/j.jnoncrysol.2022.122009)
  DOI : 10.1016/j.jnoncrysol.2022.122009
• Electron acceleration by laser plasma wedge interaction
  
  • Marini S.
  • Kleij P.S.
  • Grech M.
  • Raynaud M.
  • Riconda C.
  Physical Review Research, American Physical Society, 2023, 5 (1), pp.013115. A new electron acceleration mechanism is identified that develops when a relativistically intense laser irradiates the wedge of an over-dense plasma. This induces a diffracted electromagnetic wave with a significant longitudinal electric field that accelerates electrons from the plasma over long distances to relativistic energies. Well collimated, highly-charged (nC) electron bunches with energies up to 100's MeV are obtained using a laser beam with $I \lambda_0^2 =3.5\times 10^{19}\,{\rm W \mu m^2/cm^2}$. Multi-dimensional particle-in-cell simulations, supported by a simple analytical model, confirm the efficiency and robustness of the proposed acceleration scheme. (10.1103/PhysRevResearch.5.013115)
  DOI : 10.1103/PhysRevResearch.5.013115
• Electrical surface properties of nanoporous alumina membranes: influence of nanochannels’ curvature, roughness and composition studied via electrokinetic experiments
  
  • Vakilinejad Ali
  • Dubois Emmanuelle
  • Michot Laurent
  • Jardat Marie
  • Lairez Didier
  • Durand-Vidal Serge
  • Guibert Clément
  • Jouault Nicolas
  Physical Chemistry Chemical Physics, Royal Society of Chemistry, 2023, 25 (41), pp.28150-28161. Among classical nanoporous oxide membranes, anodic aluminum oxide (AAO) membranes, made of non-connected, parallel and ordered nanochannels, are very interesting nanoporous model systems widely used for multiple applications. Since most of these applications involve local phenomena at the nanochannel surface, the fine description of the electrical surface behavior in aqueous solution is thus of primordial interest. Here, we use an original experimental approach combining several electrokinetic techniques (tangential and transverse streaming potential as well as electrophoretic mobility experiments) to measure the ζ-potential and determine the surface isoelectric points (IEPs) of several AAOs having different characteristic sizes and compositions. Using such an approach, all the different surfaces available in AAOs can be probed: outer surfaces (top and bottom planes), pore wall surfaces (i.e., inner surfaces) and surfaces created by the grinding of the AAOs. We find clear IEP differences between the outer, pore wall and ground surfaces and discuss these in terms of nanochannel and surface morphology (curvature and roughness) and of modifications of the chemical environment of the surface hydroxyl groups. These results highlight the heterogeneities between the different surfaces of these AAO membranes and emphasize the necessity to combine complementary electrokinetic techniques to properly understand the material, an approach which can be extended to many nanoporous systems. (10.1039/D3CP04067D)
  DOI : 10.1039/D3CP04067D
• Electronic dispersion, correlations and stacking in the photoexcited state of 1T-TaS2
  
  • Dong Jingwei
  • Shin Dongbin
  • Pastor Ernest
  • Ritschel Tobias
  • Cario Laurent
  • Chen Zhesheng
  • Qi Weiyan
  • Grasset Romain
  • Marsi Marino
  • Taleb-Ibrahimi Amina
  • Park Noejung
  • Rubio Angel
  • Perfetti Luca
  • Papalazarou Evangelos
  2D Materials, IOP Publishing, 2023, 10 (4), pp.045001. Here we perform angle and time-resolved photoelectron spectroscopy on the commensurate charge density wave (CDW) phase of 1T-TaS 2 . Data with different probe pulse polarization are employed to map the dispersion of electronic states below and above the chemical potential. Upon photoexcitation, the fluctuations of CDW order erase the band dispersion and squeeze the electronic states near to the chemical potential. This transient phase sets within half a period of the coherent lattice motion and is favored by strong electronic correlations. The experimental results are compared to density-functional theory calculations with a self-consistent evaluation of the Coulomb repulsion. Our simulations indicate that the screening of Coulomb repulsion depends on the stacking order of the TaS 2 layers. The entanglement of such degrees of freedom suggest that both the structural order and electronic repulsion are locally modified by the photoinduced CDW fluctuations. (10.1088/2053-1583/ace374)
  DOI : 10.1088/2053-1583/ace374
• From selective dissolution to crystal chemistry of brownmillerite in sulfate resisting cement
  
  • Mériot Alexis
  • de Noirfontaine Marie‐noëlle
  • Courtial Mireille
  • Izoret Laurent
  • Tusseau-Nenez Sandrine
  • Labourel Mélanie
  • Gauffinet sandrine
  • Dunstetter Frédéric
  Journal of the American Ceramic Society, Wiley, 2023, 106, pp.709-721. The aim of this study is to extract brownmillerite from sulfate resisting Portland cement (SRPC) in order to determine its crystal chemistry and the effects of dissolution protocols. Brownmillerites (C4AF) from four SRPC were extracted and systematically studied by X-ray diffraction (XRD), electron probe microanalysis (EPMA) and X-ray fluorescence spectroscopy. Two extraction steps were used. The first is the SAM protocol that leaves a residue rich in ferrite, C3A and sulfates. Precipitated hydrated sulfate minerals are also observed for clinker with high molar SO3/Na2Oeq ratio. The second, developed in this paper, uses acetic acid (AcA) to dissolve C3A and sulfates. The Rietveld refinements showed that all brownmillerites of this study crystallize in Ibm2 space group. Two families of brownmillerite were identified by their aluminum content and cell parameters, related to the presence of C3A in the clinker. EPMA indicated that ferrites from SR0 and SR3 cements have Al/Fe ratios about 0.7 and 0.8-1.0 respectively. XRD allows to predict the (Al+Mg+Si)/Fe ratio in brownmillerite in good agreement with EPMA. The SAM protocol is the best way to study crystal chemistry of brownmillerite and the AcA protocol is recommended to dissolve sulfates and C3A for further reactivity studies. (10.1111/jace.18764)
  DOI : 10.1111/jace.18764
• Enhanced magnetic modulation of surface plasmon polaritons on hyperbolic metasurfaces
  
  • Kuzmin Dmitry
  • Usik Maksim
  • Bychkov Igor
  • Bugaev Aleksandr
  • Shavrov Vladimir
  • Temnov Vasily
  Optics Letters, Optical Society of America - OSA Publishing, 2023, 48 (13), pp.3479. In this Letter we demonstrate a fundamentally new, to the best of our knowledge, concept to enhance the magnetic modulation of the surface plasmon polaritons (SPPs) by using hybrid magneto-plasmonic structures consisting of hyperbolic plasmonic metasurfaces and magnetic dielectric substrates. Our results show that the magnetic modulation of SPPs in the proposed structures can be an order of magnitude stronger than in the hybrid metal-ferromagnet multilayer structures conventionally used in active magneto-plasmonics. We believe that this effect will allow for the further miniaturization of magneto-plasmonic devices. (10.1364/OL.493787)
  DOI : 10.1364/OL.493787
• Pseudopotential Bethe-Salpeter calculations for shallow-core x-ray absorption near-edge structures: Excitonic effects in α − Al 2 O 3
  
  • Urquiza M. Laura
  • Gatti Matteo
  • Sottile Francesco
  Physical Review B, American Physical Society, 2023, 107 (20), pp.205148. We present an ab initio description of optical and shallow-core x-ray absorption spectroscopies in a unified formalism based on the pseudopotential plane-wave method at the level of the Bethe-Salpeter equation (BSE) within Green's functions theory. We show that norm-conserving pseudopotentials are reliable and accurate not only for valence, but also for semicore electron excitations. In order to validate our approach, we compare BSE absorption spectra obtained with two different codes: the pseudopotential-based code EXC and the all-electron full-potential code Exciting. We take corundum $\alpha$-Al$_2$O$_3$ as an example, being a prototypical material that presents strong electron-hole interactions for both valence and core electron excitations. We analyze in detail the optical absorption spectrum as well as the Al L$_1$ and L$_{2,3}$ edges in terms of anisotropy, crystal local fields, interference and excitonic effects. We perform a thorough inspection of the origin and localization of the lowest-energy excitons, and conclude highlighting the purely electronic character off the pre-edge of L$_1$ and the dichroic nature of the optical and L$_{23}$ spectra. (10.1103/PhysRevB.107.205148)
  DOI : 10.1103/PhysRevB.107.205148
• Dynamics of electronic states in the insulating intermediate surface phase of 1T−TaS$_2$
  
  • Dong Jinwei
  • Qi Weiyan
  • Shin Dongbin
  • Cario Laurent
  • Chen Zhesheng
  • Grasset Romain
  • Boschetto Davide
  • Weis Mateusz
  • Lample Pierrick
  • Pastor Ernest
  • Ritschel Tobias
  • Marsi Marino
  • Taleb-Ibrahimi Amina
  • Park Noejung
  • Rubio Angel
  • Papalazarou Evangelos
  • Perfetti Luca
  Physical Review B, American Physical Society, 2023, 108 (15), pp.155145. This article reports a comparative study of bulk and surface properties in the transition metal dichalcogenide 1T−TaS$_2$. When heating the sample, the surface displays an intermediate insulating phase that persists for ∼10 K on top of a metallic bulk. The weaker screening of Coulomb repulsion and a stiffer charge density wave (CDW) explain such resilience of a correlated insulator in the topmost layers. Both time-resolved angle-resolved photoelectron spectroscopy and transient reflectivity are employed to investigate the dynamics of electrons and CDW collective motion. It follows that the amplitude mode is always stiffer at the surface and displays variable coupling to the Mott-Peierls band, stronger in the low-temperature phase and weaker in the intermediate one. (10.1103/physrevb.108.155145)
  DOI : 10.1103/physrevb.108.155145
• Bulk evidence of anisotropic s-wave pairing with no sign change in the kagome superconductor CsV3Sb5
  
  • Roppongi M.
  • Ishihara K.
  • Tanaka Y.
  • Ogawa K
  • Okada K
  • Liu S
  • Mukasa K
  • Mizukami Y
  • Uwatoko Y
  • Grasset R
  • Konczykowski M
  • Ortiz B R
  • Wilson S D
  • Hashimoto K
  • Shibauchi T
  Nature Communications, Nature Publishing Group, 2023, 14, pp.667. The recently discovered kagome superconductors AV3Sb5 (A = K, Rb, Cs) exhibit unusual charge-density-wave (CDW) orders with time-reversal and rotational symmetry breaking. One of the most crucial unresolved issues is identifying the symmetry of the superconductivity that develops inside the CDW phase. Theory predicts a variety of unconventional superconducting symmetries with sign-changing and chiral order parameters. Experimentally, however, superconducting phase information in AV3Sb5 is still lacking. Here we report the impurity effects in CsV3Sb5 using electron irradiation as a phase-sensitive probe of superconductivity. Our magnetic penetration depth measurements reveal that with increasing impurities, an anisotropic fully-gapped state changes to an isotropic full-gap state without passing through a nodal state. Furthermore, transport measurements under pressure show that the double superconducting dome in the pressure-temperature phase diagram survives against sufficient impurities. These results support that CsV3Sb5 is a non-chiral, anisotropic s-wave superconductor with no sign change both at ambient and under pressure. (10.1038/s41467-023-36273-x)
  DOI : 10.1038/s41467-023-36273-x