Publications

2023

• Paramagnetic Point Defect in Fluorine-Doped Silica Glass: The E ′ ( F ) Center
  
  • Skuja Linards
  • Leimane Madara
  • Ollier Nadège
  • Grishchenko Andrey
  Physical Review Letters, American Physical Society, 2023, 131 (25), pp.256903. (10.1103/PhysRevLett.131.256903)
  DOI : 10.1103/PhysRevLett.131.256903
• A multiparametric study on the behavior of mesoporous silica under electron irradiation
  
  • Lin Jun
  • Grygiel Clara
  • Alessi Antonino
  • Dourdain Sandrine
  • Causse Jérémy
  • Ollier Nadège
  • Cavani Olivier
  • Rey Cyrielle
  • Toquer Guillaume
  • Deschanels Xavier
  Materialia, Elsevier, 2023, 32, pp.101903. Grafted mesoporous silica is believed to be a candidate for the decontamination of radioactive effluents and the final storage of radionuclides. Under this condition, silica is subjected to continuous electron irradiation due to beta decay of radionuclides. This paper examined two mesoporous silica (SBA-15 and MCM-41) under high-energy electron beam irradiation (0.6 MeV < E < 2.4 MeV). The results showed that the pore structure of both mesoporous silica pellets shrank for all the samples (with 40 % < ΔVpores < 60 % at 8 × 1018 e-/cm2), while no significant damage was observed in the amorphous silica network. The main reason for the structural changes was attributed to electron beam radiation-induced fluidization. Additional experiments conducted with numerous incident electron energies provided more detailed support, confirming that the radiolytic process was the primary cause of fluidization. These findings contribute to a better understanding of electron-irradiation-induced damage and may lead to novel approaches for handling radionuclides with mesoporous materials. (10.1016/j.mtla.2023.101903)
  DOI : 10.1016/j.mtla.2023.101903
• Ultrasmall and tunable TeraHertz surface plasmon cavities at the ultimate plasmonic limit
  
  • Aupiais Ian
  • Grasset Romain
  • Guo Tingwen
  • Daineka Dmitri
  • Briatico Javier
  • Houver Sarah
  • Perfetti Luca
  • Hugonin Jean-Paul
  • Greffet Jean-Jacques
  • Laplace Yannis
  Nature Communications, Nature Publishing Group, 2023, 14 (1), pp.7645. Abstract The ability to confine THz photons inside deep-subwavelength cavities promises a transformative impact for THz light engineering with metamaterials and for realizing ultrastrong light-matter coupling at the single emitter level. To that end, the most successful approach taken so far has relied on cavity architectures based on metals, for their ability to constrain the spread of electromagnetic fields and tailor geometrically their resonant behavior. Here, we experimentally demonstrate a comparatively high level of confinement by exploiting a plasmonic mechanism based on localized THz surface plasmon modes in bulk semiconductors. We achieve plasmonic confinement at around 1 THz into record breaking small footprint THz cavities exhibiting mode volumes as low as $${V}_{cav}/{\lambda }_{0}^{3} \sim 1{0}^{-7}-1{0}^{-8}$$ V c a v / λ 0 3 ~ 1 0 − 7 − 1 0 − 8 , excellent coupling efficiencies and a large frequency tunability with temperature. Notably, we find that plasmonic-based THz cavities can operate until the emergence of electromagnetic nonlocality and Landau damping, which together constitute a fundamental limit to plasmonic confinement. This work discloses nonlocal plasmonic phenomena at unprecedentedly low frequencies and large spatial scales and opens the door to novel types of ultrastrong light-matter interaction experiments thanks to the plasmonic tunability. (10.1038/s41467-023-43394-w)
  DOI : 10.1038/s41467-023-43394-w
• CdZnTe Crystal Quality Study by Cathodoluminescence Measurements
  
  • Léger Valentin
  • Bidaud Thomas
  • Collin Stéphane
  • Patriarche Gilles
  • Corbel Catherine
  • Rubaldo Laurent
  Journal of Electronic Materials, Institute of Electrical and Electronics Engineers, 2023, 52 (11), pp.7054-7059. Improving material quality is an essential step to maintain high electro-optical performance at higher operating temperature (HOT) of cooled II-VI infrared (IR) detectors. Indeed, the electrical activity of crystal defects affects their image quality and stability. A first investigation is to correlate the point defect populations with the crystal quality of the Cd1−xZnxTe (CZT) substrate, used for the growth of the Hg1−xCdxTe (MCT) active layer. For this purpose, spectrally resolved cathodoluminescence (CL) measurements were performed for wafers with low and high crystal quality, with a respective dislocation density of 1.8 × 104 cm−2 and 6 × 103 cm−2. At 295 K, both wafers showed band-to-band transition, and CL spectra were modeled with the generalized Planck law. However, at 10 K, CL spectra showed that the visibility of phonon replicas of the donor–acceptor pair () transition at 1.57 eV is dependent on the crystalline order. In addition, the luminescence of the A-center defect () was observed at 1.43 eV only in the low-quality CZT substrate. (10.1007/s11664-023-10566-9)
  DOI : 10.1007/s11664-023-10566-9
• Quantitative Ultrafast Magnetoacoustics at Magnetic Metasurfaces
  
  • Alekhin Alexandr
  • Lomonosov Alexey
  • Leo Naëmi
  • Ludwig Markus
  • Vlasov Vladimir
  • Kotov Leonid
  • Leitenstorfer Alfred
  • Gaal Peter
  • Vavassori Paolo
  • Temnov Vasily
  Nano Letters, American Chemical Society, 2023. Femtosecond (fs) time-resolved magneto-optics is applied to investigate laser-excited ultrafast dynamics of one-dimensional nickel gratings on fused silica and silicon substrates for a wide range of periodicities Λ = 400–1500 nm. Multiple surface acoustic modes with frequencies up to a few tens of GHz are generated. Nanoscale acoustic wavelengths Λ/n have been identified as nth-spatial harmonics of Rayleigh surface acoustic wave (SAW) and surface skimming longitudinal wave (SSLW), with acoustic frequencies and lifetimes being in agreement with theoretical calculations. Resonant magnetoelastic excitation of the ferromagnetic resonance (FMR) by SAW’s third spatial harmonic, and, most interestingly fingerprints of the parametric resonance at 1/2 SAW frequency have been observed. Numerical solutions of Landau–Lifshitz–Gilbert (LLG) equation magnetoelastically driven by complex polychromatic acoustic fields quantitatively reproduce all resonances at once. Thus, our results provide a solid experimental and theoretical base for a quantitative understanding of ultrafast fs-laser-driven magnetoacoustics and tailoring the magnetic-grating-based metasurfaces at the nanoscale. (10.1021/acs.nanolett.3c02336)
  DOI : 10.1021/acs.nanolett.3c02336
• Electron irradiation: From test to material tailoring
  
  • Alessi A.
  • Cavani O.
  • Grasset R.
  • Drouhin H.-J.
  • Safarov V.
  • Konczykowski M.
  EPL - Europhysics Letters, European Physical Society / EDP Sciences / Società Italiana di Fisica / IOP Publishing, 2023, 143 (5), pp.56001. Abstract In this article, we report some examples of how high-energy electron irradiation can be used as a tool for shaping material properties turning the generation of point-defects into an advantage beyond the presumed degradation of the properties. Such an approach is radically different from what often occurs when irradiation is used as a test for radiation hard materials or devices degradation in harsh environments. We illustrate the potential of this emerging technique by results obtained on two families of materials, namely semiconductors and superconductors. (10.1209/0295-5075/acf47c)
  DOI : 10.1209/0295-5075/acf47c
• Ab initio nonlinear optics in solids : Linear Electro-Optic Effect and Electric-Field Induced Second-Harmonic Generation
  
  • Prussel Lucie
  • Maji Rita
  • Degoli Elena
  • Luppi Eleonora
  • Véniard Valérie
  The European Physical Journal. Special Topics, EDP Sciences / Springer Verlag, 2023, 232, pp.2231-2240. Second-harmonic generation (SHG), linear electro-optic effect (LEO) and electric-field induced second-harmonic generation (EFISH) are nonlinear optical processes with important applications in optoelectronics and photovoltaics. SHG and LEO are second-order nonlinear optical processes described by second-order susceptibility. Instead, EFISH is a third-order nonlinear optical process described by third-order susceptibility. LEO and EFISH are only observed in the presence of a static electric field. These nonlinear processes are very sensitive to the symmetry of the systems. In particular, LEO is usually observed through a change in the dielectric properties of the material while EFISH can be used to generate a “second harmonic” response in centrosymmetric material. In this work, we present a first-principle formalism to calculate second- and third-order susceptibility for LEO and EFISH. LEO is studied for GaAs semiconductor and compared with the dielectric properties of this material. We also present how it is possible for LEO to include the ionic contribution to the second-order macroscopic susceptibility. Concerning EFISH we present for the first time the theory we developed in the framework of TDDFT to calculate this nonlinear optical process. Our approach permits to obtain an expression for EFISH which does not contain the mathematical divergences in the frequency-dependent second-order susceptibility that caused until now many difficulties for numerical calculations. (10.1140/epjs/s11734-022-00677-5)
  DOI : 10.1140/epjs/s11734-022-00677-5
• Tunable 3D luminescence patterns in glass with a femtosecond laser
  
  • Alassani Fouad
  • Ollier Nadège
  • Raffy Guillaume
  • Galleani Gustavo
  • Stucchi de Camargo Andrea Simone
  • Canioni Lionel
  • Cardinal Thierry
  • Petit Yannick
  , 2023.
• Probing densified silica glass structure by molecular oxygen and E’ center formation under electron irradiation
  
  • Ollier N.
  • Reghioua I.
  • Cavani O.
  • Mobasher M.
  • Alessi A.
  • Le Floch Sylvie
  • Skuja L.
  Scientific Reports, Nature Publishing Group, 2023, 13 (1), pp.13657. Abstract This study aims to learn more about the structure of densified silica with focus on the metamict-like silica phase (density = 2.26 g/cm 3 ) by examining the formation of E’ point defects and interstitial molecular oxygen O 2 by 2.5 MeV electron irradiation. High-dose (11 GGy) irradiation creates a metamict-like phase and a large amount of interstitial O 2 , which is destroyed upon subsequent additional lower-dose electron irradiation. The O 2 cathodoluminescence (CL) data indicate that the formation of O 2 from peroxy linkages Si–O–O–Si in silica network is strongly dependent on the intertetrahedral void sizes. The position and shape of the O 2 emission line support the idea that the configuration of these voids in metamict phase is close to that of non-densified silica. Moreover, data support the strong correlation between the formation of 3-membered rings of Si–O bonds and E’-centers when silica density increases from 2.20 to 2.26 g/cm 3 . (10.1038/s41598-023-40270-x)
  DOI : 10.1038/s41598-023-40270-x
• Role of Dimensionality and Size in Governing the Drag Seebeck Coefficient of Doped Silicon Nanostructures: A Fundamental Understanding
  
  • Sen Raja
  • Vast Nathalie
  • Sjakste Jelena
  Physical Review B, American Physical Society, 2023, 108 (6), pp.L060301. In this theoretical study, we examine the influence of dimensionality, size reduction, and heattransport direction on the phonon-drag contribution to the Seebeck coefficient of silicon nanostructures. Phonon-drag contribution arises from the momentum transfer between out-of-equilibrium phonon populations and charge carriers, and significantly enhances the thermoelectric coefficient. Our implementation of the phonon drag term accounts for the anisotropy of nanostructures such as thin films and nanowires through the boundary-and momentum-resolved phonon lifetime. Our approach also takes into acconout the spin-orbit coupling, which turns out to be crucial for hole transport. We reliably quantify the phonon drag contribution at various doping levels, temperatures, and nanostructure geometries for both electrons and holes in silicon nanstructures. Our results support the recent experimental findings, showing that a part of phonon drag contribution survives in 100 nm silicon nanostructures. (10.1103/PhysRevB.108.L060301)
  DOI : 10.1103/PhysRevB.108.L060301
• Theoretical Raman spectrum of boron carbide B4.3C under pressure
  
  • Jay Antoine
  • Hardouin Duparc Olivier
  • Sjakste Jelena
  • Vast Nathalie
  Acta Materialia, Elsevier, 2023, 255, pp.119085. The most striking features of the Raman spectrum of boron carbide under pressure are explained theoretically by computing the Raman tensor using density functional perturbation theory and the second-order response. While the observed pressure-induced changes in frequencies and intensities of all of the peaks above 450 cm−1 are convincingly explained by the vibrations of (B11C) icosahedra and C-B-C chains – that have been identified for long as the two main components of the atomic structure of pristine B4C –, the puzzling non-monotonic behavior of a broad Raman band at low frequency, whose intensity increases under pressure up to 44 GPa, decreases and then vanishes, was so far unexplained. We find that the behavior under pressure of both the frequency and intensity of this band turns out to be remarkably accounted for, in the calculations, by the activation of the chain bending mode in atypically flexured chains. We show that the flexion of the chain occurs at high pressure in presence of interstitial B atoms that, at ambient pressure, sit in the prolongation of standard C-B-C chains. We propose the ambient-P mode observed at 270 cm−1 as a fingerprint for the identification of both such B-C-B-C chain-defects in boron carbide and local deviations from the rhombohedral symmetry. (10.1016/j.actamat.2023.119085)
  DOI : 10.1016/j.actamat.2023.119085
• Improvement of ZnGeP2 optical quality by investigating growth conditions and high energy electron irradiation
  
  • Vernozy C.
  • Alessi A.
  • Courpron A.
  • Veniard V.
  • Petit J.
  , 2023.
• Towards resonantly enhanced acoustic phonon-exchange magnon interactions at THz frequencies
  
  • Mocioi Tudor-Gabriel
  • Ghita Antonia
  • Temnov Vasily V
  Magnetochemistry, MDPI, 2023, 9, pp.184. Using valid experimental parameters, we quantify the magnitude of resonantly phonondriven precession of exchange magnons in freestanding ferromagnetic nickel thin films on their thickness L. Analytical solutions of acoustically driven equations for magnon oscillators display a nonmonotonous dependence of the peak magnetization precession on the film thickness. It is explained by different L-dependence of multiple prefactors entering in the expression for the total magnetization dynamics. Depending on the ratio of acoustic and magnetic (Gilbert) damping constants, the magnetization precession is shown to be amplified by a Q-factor of either the phonon or the magnon resonance. The increase in the phonon mode amplitude for thinner membranes is also found to be significant. Focusing on the magnetization dynamics excited by the two first acoustic eigenmodes with p = 1 and p = 2, we predict the optimum thicknesses of nickel membranes to achieve large amplitude magnetization precession at multi 100 GHz frequencies at reasonably low values of an external magnetic field. By extending the study to the case of Ni-Si bilayers, we show that these resonances are achievable at even higher frequencies, approaching the THz range. (10.3390/magnetochemistry9070184)
  DOI : 10.3390/magnetochemistry9070184
• Towards Resonantly Enhanced Acoustic Phonon-Exchange Magnon Interactions at THz Frequencies
  
  • Mocioi Tudor-Gabriel
  • Ghita Antonia
  • Temnov Vasily
  Magnetochemistry, MDPI, 2023, 9 (7), pp.184. Using valid experimental parameters, we quantify the magnitude of resonantly phonon-driven precession of exchange magnons in freestanding ferromagnetic nickel thin films on their thickness L. Analytical solutions of acoustically driven equations for magnon oscillators display a nonmonotonous dependence of the peak magnetization precession on the film thickness. It is explained by different L-dependence of multiple prefactors entering in the expression for the total magnetization dynamics. Depending on the ratio of acoustic and magnetic (Gilbert) damping constants, the magnetization precession is shown to be amplified by a Q-factor of either the phonon or the magnon resonance. The increase in the phonon mode amplitude for thinner membranes is also found to be significant. Focusing on the magnetization dynamics excited by the two first acoustic eigenmodes with p=1 and p=2, we predict the optimum thicknesses of nickel membranes to achieve large amplitude magnetization precession at multi 100 GHz frequencies at reasonably low values of an external magnetic field. By extending the study to the case of Ni-Si bilayers, we show that these resonances are achievable at even higher frequencies, approaching the THz range. (10.3390/magnetochemistry9070184)
  DOI : 10.3390/magnetochemistry9070184
• Femtosecond Laser Ablation-Induced Magnetic Phase Transformations in FeRh Thin Films
  
  • Varlamov Pavel
  • Semisalova Anna
  • Nguyen Anh Dung
  • Farle Michael
  • Laplace Yannis
  • Raynaud Michele
  • Noel Olivier
  • Vavassori Paolo
  • Temnov Vasily
  Magnetochemistry, MDPI, 2023, 9 (7), pp.186. In this study, we present a novel investigation into the magnetic and morphological properties of equiatomic B2-ordered FeRh thin films irradiated with single high-intensity ultrashort laser pulses. The goal is to elucidate the effect of femtosecond laser ablation on the magnetic properties of FeRh. We employed Scanning Magneto-Optical Kerr Effect (S-MOKE) microscopy to examine the magnetic phase after laser processing, providing high spatial resolution and sensitivity. Our results for the first time demonstrated the appearance of a magneto-optical signal from the bottom of ablation craters, suggesting a transition from antiferromagnetic to ferromagnetic behavior. Fluence-resolved measurements clearly demonstrate that the ablation threshold coincides with the threshold of the antiferromagnet-to-ferromagnet phase transition. The existence of such a magnetic phase transition was independently confirmed by temperature-dependent S-MOKE measurements using a CW laser as a localized heat source. Whereas the initial FeRh film displayed a reversible antiferromagnet-ferromagnet phase transition, the laser-ablated structures exhibited irreversible changes in their magnetic properties. This comprehensive analysis revealed the strong correlation between the femtosecond laser ablation process and the magnetic phase transformation in FeRh thin films. (10.3390/magnetochemistry9070186)
  DOI : 10.3390/magnetochemistry9070186
• Effects of beta ray irradiation on 4H-SiC epitaxial layer probed by exciton recombination
  
  • Migliore F.
  • Alessi A.
  • Principato F.
  • Girard S.
  • Morana A.
  • Cannas M.
  • Gelardi F. M.
  • Lombardo A.
  • Vecchio D.
  • Brischetto A.
  • Agnello S.
  , 2023.
• Silver photochemical reactivity analysis in electron-irradiated gallo-phosphate glasses
  
  • Alassani Fouad
  • Petit Yannick
  • Canioni Lionel
  • Ollier Nadège
  , 2023.
• Response of epitaxial layer of 4H-SiC to β-rays and X-rays irradiation
  
  • Migliore Francesca
  • Alessi Antonino
  • Principato Fabio
  • Girard Sylvain
  • Morana Adriana
  • Cannas Marco
  • Gelardi Franco M.
  • Lombardo Alice
  • Vecchio Daniele
  • Brischetto Andrea
  • Agnello Simonpietro
  , 2023.
• Author Correction: Subpicosecond metamagnetic phase transition in FeRh driven by non-equilibrium electron dynamics
  
  • Pressacco Federico
  • Sangalli Davide
  • Uhlíř Vojtěch
  • Kutnyakhov Dmytro
  • Arregi Jon Ander
  • Agustsson Steinn Ymir
  • Brenner Günter
  • Redlin Harald
  • Heber Michael
  • Vasilyev Dmitry
  • Demsar Jure
  • Schönhense Gerd
  • Gatti Matteo
  • Marini Andrea
  • Wurth Wilfried
  • Sirotti Fausto
  Nature Communications, Nature Publishing Group, 2023, 14 (1). Correction to: Nature Communications https://doi.org/10.1038/s41467-021-25347-3, published online 24 August 2021 In the authors final submission, the Supplementary Information was uploaded as a ZIP file, containing a non-compliable TeX file, rather than in PDF or word document. The Supplementary movies referred to within the text were not included in the final version as part of the Supplementary Information ZIP file. The attached files are the correct versions of the Supplementary Information and Supplementary movies referred to in the text, contained in the attached ZIP file and contain no changes. (10.1038/s41467-023-38263-5)
  DOI : 10.1038/s41467-023-38263-5
• Accurate Kohn-Sham auxiliary system from the ground state density of solids
  
  • Aouina Ayoub
  • Gatti Matteo
  • Chen Siyuan
  • Zhang Shiwei
  • Reining Lucia
  Physical Review B, American Physical Society, 2023, 107 (19), pp.195123. The Kohn-Sham (KS) system is an auxiliary system whose effective potential is unknown in most cases. It is in principle determined by the ground state density, and it has been found numerically for some low-dimensional systems by inverting the KS equations starting from a given accurate density. For solids, only approximate results are available. In this work, we determine accurate exchange correlation (xc) potentials for Si and NaCl using the ground state densities obtained from Auxiliary Field Quantum Monte Carlo calculations. We show that these xc potentials can be rationalized as an ensemble of a few local functions of the density, whose form depends on the specific environment and can be well characterised by the gradient of the density and the local kinetic energy density. The KS band structure can be obtained with high accuracy. The true KS band gap turns out to be larger than the prediction of the local density approximation, but significantly smaller than the measurable photoemission gap, which confirms previous estimates. Finally, our findings show that the conjecture that very different xc potentials can lead to very similar densities and other KS observables is true also in solids, which questions the meaning of details of the potentials and, at the same time, confirms the stability of the KS system. (10.1103/PhysRevB.107.195123)
  DOI : 10.1103/PhysRevB.107.195123
• Plasmonic Polarization Rotation in SERS Spectroscopy
  
  • Xiao Xiaofei
  • Gillibert Raymond
  • Foti Antonino
  • Coulon Pierre-Eugène
  • Ulysse Christian
  • Levato Tadzio
  • Maier Stefan
  • Giannini Vincenzo
  • Gucciardi Pietro Giuseppe
  • Rizza Giancarlo
  Nano Letters, American Chemical Society, 2023, 23 (7), pp.2530-2535. Surface-enhanced Raman optical activity (SEROA) has been extensively investigated due to its ability to directly probe stereochemistry and molecular structure. However, most works have focused on the Raman optical activity (ROA) effect arising from the chirality of the molecules on isotropic surfaces. Here, we propose a strategy for achieving a similar effect: i.e., a surface-enhanced Raman polarization rotation effect arising from the coupling of optically inactive molecules with the chiral plasmonic response of metasurfaces. This effect is due to the optically active response of metallic nanostructures and their interaction with molecules, which could extend the ROA potential to inactive molecules and be used to enhance the sensibility performances of surface-enhanced Raman spectroscopy. More importantly, this technique does not suffer from the heating issue present in traditional plasmonic-enhanced ROA techniques, as it does not rely on the chirality of the molecules. (10.1021/acs.nanolett.2c04461)
  DOI : 10.1021/acs.nanolett.2c04461
• Optical properties of quasi-two-dimensional objects from time-dependent density functional theory: Longitudinal versus transverse dielectric functions
  
  • Mazzei Stefano
  • Giorgetti Christine
  Physical Review B, American Physical Society, 2023, 107 (16), pp.165412. Comprehension of the electronic properties of nano-objects is a key to defining dedicated properties, which can be adjusted by changing their size. Beyond confinement effects, the presence of interfaces, i.e., places where there is an abrupt change of electronic density, should also play a role. Time-dependent density functional theory (TD-DFT) is a state-of-the-art ab initio formalism in which this effect is accounted for through the so-called local field effects. In an earlier paper [S. Mazzei and C. Giorgetti, Phys. Rev. B 106, 035431 (2022)], we showed that the framework inherited from three-dimensional crystals could not provide reliable absorption spectra. In the present paper, we propose to calculate the macroscopic average of the dielectric tensor of a quasi-twodimensional (2D) object from the response function of the density to the total macroscopic potential in order to avoid use of the so-called Adler and Wiser formula. We evidence that the inclusion of interfaces in the thickness of the slab causes the response function for the out-of-plane component to move sharply from the bulk absorption resonance to the plasmon one. This shows that the longitudinal-longitudinal contraction of the dielectric tensor is no longer equal to the transverse-transverse one in a quasi-2D object for out-of-plane perturbation. Nevertheless, we also show that the macroscopic average of the dielectric tensor of an ultrathin slab calculated within the longitudinal formalism of TD-DFT depicts the properties of the transverse reflectance and transmittance spectra of a thin slab. (10.1103/PhysRevB.107.165412)
  DOI : 10.1103/PhysRevB.107.165412
• Anatomy of ultrafast quantitative magnetoacoustics in freestanding nickel thin films
  
  • Ghita Antonia
  • Mocioi Tudor-Gabriel
  • Lomonosov Alexey
  • Kim Jiwan
  • Kovalenko Oleksandr
  • Vavassori Paolo
  • Temnov Vasily
  Physical Review B, American Physical Society, 2023, 107 (13), pp.134419. We revisit the quantitative analysis of the ultrafast magnetoacoustic experiment in a freestanding nickel thin film by Kim and Bigot [J.-W. Kim and J.-Y. Bigot, Phys. Rev. B 95, 144422 (2017)] by applying our recently proposed approach of magnetic and acoustic eigenmode decomposition. We show that the application of our modeling to the analysis of time-resolved reflectivity measurements allows for the determination of amplitudes and lifetimes of standing perpendicular acoustic phonon resonances with unprecedented accuracy. The acoustic damping is found to scale as ∝ω2 for frequencies up to 80 GHz, and the peak amplitudes reach 10−3. The experimentally measured magnetization dynamics for different orientations of an external magnetic field agrees well with numerical solutions of magnetoelastically driven magnon harmonic oscillators. Symmetry-based selection rules for magnon-phonon interactions predicted by our modeling approach allow for the unambiguous discrimination between spatially uniform and nonuniform modes, as confirmed by comparing the resonantly enhanced magnetoelastic dynamics simultaneously measured on opposite sides of the film. Moreover, the separation of timescales for (early) rising and (late) decreasing precession amplitudes provide access to magnetic (Gilbert) and acoustic damping parameters in a single measurement. (10.1103/PhysRevB.107.134419)
  DOI : 10.1103/PhysRevB.107.134419
• Manipulating Dirac states in BaNiS$_2$ by surface charge doping
  
  • Zhang Jiuxiang
  • Sohier Thibault Daniel Pierre
  • Casula Michele
  • Chen Zhesheng
  • Caillaux Jonathan
  • Papalazarou Evangelos
  • Perfetti Luca
  • Petaccia Luca
  • Bendounan Azzedine
  • Taleb-Ibrahimi Amina
  • Santos-Cottin David
  • Klein Yannick
  • Gauzzi Andrea
  • Marsi Marino
  Nano Letters, American Chemical Society, 2023, 23 (5), pp.1830-1835. In the Dirac semimetal BaNiS$_2$ , the Dirac nodes are located along the Γ − M symmetry line of the Brillouin zone, instead of being pinned at fixed high-symmetry points. We take advantage of this peculiar feature to demonstrate the possibility of moving the Dirac bands along the Γ − M symmetry line in reciprocal space by varying the concentration of K atoms adsorbed onto the surface of cleaved BaNiS$_2$ single crystals. By means of first-principles calculations, we give full account for this observation by considering the effect of the electrons donated by the K atom on the charge transfer gap, which establishes a promising tool for engineering Dirac states at surfaces, interfaces and heterostructures. (10.1021/acs.nanolett.2c04701)
  DOI : 10.1021/acs.nanolett.2c04701
• Two-dimensional fluctuations and competing phases in the stripe-like antiferromagnet BaCoS$_{2}$
  
  • Zhang Jiuxiang
  • Chen Zhesheng
  • Caillaux Jonathan
  • Klein Yannick
  • Gauzzi Andrea
  • Bendounan Azzedine
  • Taleb-Ibrahimi Amina
  • Perfetti Luca
  • Papalazarou Evangelos
  • Marsi Marino
  The European Physical Journal. Special Topics, EDP Sciences / Springer Verlag, 2023. By means of a combined x-ray diffraction, magnetic susceptibility and specific heat study, we investigate the interplay between orthorhombic distortion and stripe-like antiferromagnetic (AFM) order in the Mott insulator BaCoS$_{2}$ at $T_N=290$ K. The data give evidence of a purely electronic AFM transition with no participation of the lattice. The observation of large thermal fluctuations in the vicinity of $T_N$ and a Schottky anomaly unveils competing ground states within a minute $\sim$1 meV energy range that differ in the orbital and spin configurations of the Co ions. This interpretation suggests that the stripe-like order results from a spontaneous symmetry breaking of the geometrically frustrated pristine tetragonal phase, which offers an ideal playground to study the driving force of multi-orbital Mott transitions without the participation of the lattice. (10.1140/epjs/s11734-022-00746-9)
  DOI : 10.1140/epjs/s11734-022-00746-9