A5061844666- Advanced Condensed Matter Physics
- Magnetic and transport properties of perovskites and related materials
- Electronic and Structural Properties of Oxides
- Rare-earth and actinide compounds
- Iron-based superconductors research
- Photorefractive and Nonlinear Optics
- 2D Materials and Applications
- Physics of Superconductivity and Magnetism
- Topological Materials and Phenomena
- Multiferroics and related materials
- Transition Metal Oxide Nanomaterials
- Photonic and Optical Devices
- Superconductivity in MgB2 and Alloys
- High-pressure geophysics and materials
- Magnetic Properties and Synthesis of Ferrites
- Nonlinear Optical Materials Research
- Ferroelectric and Piezoelectric Materials
- Iron oxide chemistry and applications
- Boron and Carbon Nanomaterials Research
- Thermal Radiation and Cooling Technologies
- Quantum, superfluid, helium dynamics
- Gas Sensing Nanomaterials and Sensors
- Graphene research and applications
- Nonlinear Optical Materials Studies
- Photonic Crystals and Applications
University of Geneva
2016-2025
STMicroelectronics (France)
2021-2022
Laboratoire de Mécanique des Sols, Structures et Matériaux
2004-2007
Université Savoie Mont Blanc
2003-2005
Laboratoire d'Annecy-le-Vieux de Physique Théorique
2004-2005
European Synchrotron Radiation Facility
1998
Abstract Many chameleons, and panther chameleons in particular, have the remarkable ability to exhibit complex rapid colour changes during social interactions such as male contests or courtship. It is generally interpreted that these are due dispersion/aggregation of pigment-containing organelles within dermal chromatophores. Here, combining microscopy, photometric videography photonic band-gap modelling, we show shift through active tuning a lattice guanine nanocrystals superficial thick...
Abstract Background Color traits in animals play crucial roles thermoregulation, photoprotection, camouflage, and visual communication, are amenable to objective quantification modeling. However, the extensive variation non-melanic pigments structural colors squamate reptiles has been largely disregarded. Here, we used an integrated approach investigate morphological basis physical mechanisms generating color tropical day geckos of genus Phelsuma . Results Combining histology, optics, mass...
Abstract Chromium triiodide, CrI 3 , is emerging as a promising magnetic two-dimensional semiconductor where spins are ferromagnetically aligned within single layer. Potential applications in spintronics arise from an antiferromagnetic ordering between adjacent layers that gives rise to spin filtering and large magnetoresistance tunnelling devices. This key feature appears only thin multilayers it not inherited bulk crystals, instead neighbouring share the same ferromagnetic orientation....
The recent observation of correlated phases in transition metal dichalcogenide moiré systems at integer and fractional filling promises new insight into metal-insulator transitions the unusual states matter that can emerge near such transitions. Here, we combine real- momentum-space mapping techniques to study superlattice effects 57.4° twisted WSe_{2} (tWSe_{2}). Our data reveal a split-off flat band derives from monolayer Γ states. Using advanced analysis, directly quantify potential our...
Abstract Two‐dimensional (2D) van der Waals magnets show strong interconnection between their electrical, magnetic, and structural properties. Here, the emergence of a luminescent transition is revealed upon crossing Néel temperature CrPS 4 , layered antiferromagnetic semiconductor. This occurs above lowest absorption level. The optical transitions are attributed to excited states t 2g orbitals Cr 3+ ions, which influenced by distortion octahedral crystal field. Specifically, vicinity...
The temperature dependence of the complex optical properties three-dimensional topological insulator Bi${}_{2}$Te${}_{2}$Se is reported for light polarized in a-b planes at ambient pressure, as well effects pressure room temperature. This material displays a semiconducting character with bulk gap ${E}_{g}\ensuremath{\simeq}300$ meV 295 K. In addition to two expected infrared-active vibrations observed planes, there an additional fine structure that attributed either removal degeneracy or...
BiTeI is a giant Rashba spin splitting system, in which non-centro symmetric topological phase has recently been suggested to appear under high pressure. We investigated the optical properties of this compound, reflectivity and transmission, pressures up $15$ GPa. The gap feature conductivity vanishes above $p \sim 9$ GPa does not reappear at least plasma edge, associated with intrinsically doped charge carriers, smeared out through transition $9$ Using pressure Raman spectroscopy, we follow...
In twisted two-dimensional (2D) magnets, the stacking dependence of magnetic exchange interaction can lead to regions ferromagnetic and antiferromagnetic interlayer order, separated by non-collinear, skyrmion-like spin textures. Recent experimental searches for these textures have focused on CrI3, known exhibit either or depending layer stacking. However, very strong uniaxial anisotropy CrI3 disfavors smooth non-collinear phases in bilayers. Here, we report observation three distinct...
Using a combination of spectroscopic ellipsometry and DC transport measurements, we determine the temperature dependence optical conductivity ${\mathrm{NdNiO}}_{3}$ ${\mathrm{SmNiO}}_{3}$ films. The spectra show appearance characteristic two-peak structure in near-infrared when material passes from metal to insulator phase. Dynamical mean-field theory calculations confirm this allow us identify these spectral changes associated electronic structure. We demonstrate that insulating phase...
Abstract Recent theoretical studies have suggested that transition metal perovskite oxide membranes can enable surface phonon polaritons in the infrared range with low loss and much stronger subwavelength confinement than bulk crystals. Such modes, however, not been experimentally observed so far. Here, using a combination of far-field Fourier-transform (FTIR) spectroscopy near-field synchrotron nanospectroscopy (SINS) imaging, we study 100 nm thick freestanding crystalline membrane SrTiO 3...
We present a comparative study of the optical properties---reflectance, transmission, and conductivity---and Raman spectra two layered bismuth-tellurohalides BiTeBr BiTeCl at 300 5 K, for light polarized in a-b planes. Despite different space groups, properties compounds are very similar. Both materials doped semiconductors, with absorption edge above gap which is lower (0.62 eV) than (0.77 eV). The same Rashba splitting observed materials. A non-Drude free carrier contribution conductivity,...
Abstract We describe a technique for interactive rendering of diffraction effects produced by biological nanostructures, such as snake skin surface gratings. Our approach uses imagery from atomic force microscopy that accurately captures the geometry nanostructures responsible structural colouration, is, colouration due to wave interference, in variety animals. develop constructs bidirectional reflection distribution functions (BRDFs) directly measured data and leverages pre‐computation...
We report a detailed study of specific heat, electrical resistivity, and optical spectroscopy in the superconducting boride ${\text{LuB}}_{12}$ $({T}_{c}=0.4\text{ }\text{K})$, compare it to higher ${T}_{c}$ compound ${\text{ZrB}}_{12}$ $({T}_{c}=6\text{ }\text{K})$. Both compounds have same structure based on enclosed metallic Lu or Zr ions oversized boron cages. The infrared reflectivity ellipsometry visible range allow us extract conductivity from 6 meV 4 eV normal state 20 280 K. By...
Three novel potassium–zinc borohydrides/chlorides are described. KZn(BH4)3 and K2Zn(BH4)xCl4–x form in ball-milled KBH4:ZnCl2 mixtures with molar ratios ranging from 1.5:1 up to 3:1. On the other hand, K3Zn(BH4)xCl5–x forms only 2:1 mixture after longer milling times. The new compounds have been studied by a combination of situ synchrotron powder diffraction, thermal analysis, Raman spectroscopy, solid state DFT calculations. Rhombohedral contains an anionic complex [Zn(BH4)3]− D3 (32)...
Charge density wave (CDW) orders in vanadium-based kagome metals have recently received tremendous attention due to their unique properties and intricate interplay with exotic correlated phenomena, topological symmetry-breaking states. However, the origin of CDW order remains a topic debate. The discovery ScV$_{6}$Sn$_{6}$, bilayer metal exhibiting an in-plane $\sqrt{3}$ x $\sqrt{3} $ $\textit{R}$30$°$ time-reversal symmetry breaking, provides novel platform explore underlying mechanism...
Phonon polaritons (PhPs), light coupled to lattice vibrations, in the highly anisotropic polar layered material molybdenum trioxide (α-MoO3) are currently focus of intense research efforts due their extreme subwavelength field confinement, directional propagation, and unprecedented low losses. Nevertheless, prior has primarily concentrated on exploiting squeezing steering capabilities α-MoO3 PhPs, without inquiring much into dominant microscopic mechanism that determines long lifetimes,...
We report the optical $(6\phantom{\rule{0.3em}{0ex}}\mathrm{meV}--4\phantom{\rule{0.3em}{0ex}}\mathrm{eV})$ properties of a boride superconductor $\mathrm{Zr}{\mathrm{B}}_{12}$ $({T}_{c}=6\phantom{\rule{0.3em}{0ex}}\mathrm{K})$ in normal state from $20\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}300\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ measured on high-quality single crystals by combination reflectivity and ellipsometry. The Drude plasma frequency interband conductivity...
We study the temperature dependence of optical conductivity rare-earth nickelate films varying composition and strain close to antiferromagnetic ordering temperature, TN. Two prominent peaks at 0.6 1.3 eV, which are characteristic insulating phase, display a small but significant increase in intensity when material passes from para- antiferromagnetic. This observation indicates presence positive feedback between (AF) bond disproportionation (BD) order. By analyzing near TN, using Landau-type...
Structural phase transitions described by Mexican hat potentials should in principle exhibit aspects of Higgs and Goldstone physics. Here, we investigate the relationship between phonons that soften at such structural Higgs- Goldstone-boson analogues associated with crystallographic potential. We show that, exception systems containing only one atom type, usual modes are represented a combination several phonon modes, lowest energy relevant symmetry having substantial contribution. Taking...
The rare earth nickelates RNiO3 are metallic at high temperatures and insulating magnetically ordered low temperatures. temperature phase has been predicted to be type II multiferroic, i.e. ferroelectric magnetic order coupled occur simultaneously. Confirmation of those ideas inhibited by the absence experimental data on single crystals. Here we report Raman spectroscopic crystals (R = Y, Er, Ho, Dy, Sm, Nd) for between 10 K 1000 K. Entering observe appearance a large number additional...
We present a comprehensive comparison of the infrared charge response two systems, characteristic classes 122 pnictide $({\text{SrFe}}_{2}{\text{As}}_{2})$ and 11 chalcogenide $({\text{Fe}}_{1.087}\text{Te})$ Fe compounds with magnetically ordered ground states. In system, magnetic phase shows decreased plasma frequency scattering, associated appearance strong midinfrared features. The different magnetic-ordering pattern, also but an increase in while no clear features appear below ordering...
Considering spin-orbit coupling, the tetragonal crystal field, and all relevant superexchange processes including quantum interference, we derive expressions for energy levels of vanadium ions in Sr${}_{2}$VO${}_{4}$. The used parameters model Hamiltonian allow us to describe well excitation spectra observed neutron scattering optical experiments at low temperatures. free exhibits a minimum which corresponds novel alternating spin-orbital order with strong thermal fluctuation orbital mixing...
We report on the optical excitation spectra in Sr$_2$VO$_4$. The phonon modes are assigned and their evolution with temperature is discussed frame of different phase transitions crossed upon cooling. Besides expected infrared-active phonons we observe two additional excitations at about 290 cm$^{-1}$ 840 which could correspond to electronic V$^{4+}$ ions. Our experimental results context recent theoretical studies this material a unique spin-orbital ground state.