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Strong second harmonic generation (SHG) in silicon nitride has been extensively studied-among others, in terms of laser-induced SHG enhancement in Si3N4 waveguides. This enhancement has been ascribed to the all-optical poling induced by the…
Polarons are quasiparticles that arise from the interaction of electrons or holes with lattice vibrations. Though polarons are well-studied across multiple disciplines, experimental observations of polarons in two-dimensional crystals are…
We analyze low-frequency vibrational modes in a two-dimensional, zero-temperature, quasistatically sheared model glass to identify a population of structural "soft spots" where particle rearrangements are initiated. The population of spots…
Fluctuating orders in solids are generally considered high-temperature precursors of broken symmetry phases. However, in some cases these fluctuations persist to zero temperature and prevent the emergence of long-range order, as for example…
The intermolecular lattice vibrations in small-molecule organic semiconductors have a strong impact on their functional properties. Existing models treat the lattice vibrations within the harmonic approximation. In this work, we use…
The main feature of amorphous materials is the presence of excess vibrational modes at low energies, giving rise to the so called "boson peak" in neutron and optical spectroscopy. These same modes manifest themselves as two level systems…
We report that the second and third harmonic signal reductions with insulator film surface coverage over a gold substrate gives a measure of the electron density in the spill out volume of the insulator, which is dubbed metal insulator gap…
Near-infrared-to-visible second harmonic generation from air-stable two-dimensional polar gallium and indium metals is described. The photonic properties of 2D metals - including the largest second-order susceptibilities reported for metals…
Using density functional molecular dynamics simulations, we analyze the broken chemical order in a GeS$_2$ glass and its impact on the dynamical properties of the glass through the in-depth study of the vibrational eigenvectors. We find…
Raman spectroscopy is a useful experimental tool to investigate local deformation and structural changes in SiO$_2$-based glasses. Using a semi-classical modelling of Raman spectra in large samples of silica glasses, we show in this paper…
High-resolution neutron-scattering measurements have been performed on bulk glasses of As2S3 and As2S3I1.65 at a spallation neutron source. For the case of As2S3, an isotopic-substitution experiment involving the S isotope has allowed some…
Glasses have a large excess of low-frequency vibrational modes in comparison with crystalline solids. We show that such a feature is a necessary consequence of the geometry generic to weakly connected solids. In particular, we analyze the…
Glasses are nonequilibrium solids with properties highly dependent on their method of preparation. In vapor-deposited molecular glasses, structural organization could be readily tuned with deposition rate and substrate temperature. Herein,…
The low-temperature properties of glasses present important differences with respect to crystalline matter. In particular, models such as the Debye model of solids, which assume the existence of an underlying regular lattice, predict that…
We have determined the vibrational properties of a sodium tetrasilicate (Na$_{2}$Si$_{4}$O$_{9}$) glass model generated by molecular dynamics simulations. The study has been carried out using a classical valence force fields approach as…
The excess low-frequency normal modes for two widely-used models of glasses were studied at zero temperature. The onset frequencies for the anomalous modes for both systems agree well with predictions of a variational argument, which is…
Stimulated Brillouin scattering recently allowed experimental excitation of surface acoustic resonances in micro-devices, enabling vibration at rates in the range of 50 MHz to 12 GHz. The experimental availability of such mechanical…
The topological nature of the disorder of glasses and supercooled liquids strongly affects their high-frequency dynamics. In order to understand its main features, we analytically studied a simple topologically disordered model, where the…
Raman scattering in the three-dimensional Dirac semimetal Cd3As2 shows an intricate interplay of electronic and phonon degrees of freedom. We observe resonant phonon scattering due to interband transitions, an anomalous anharmonicity of…
We report on first direct observation of spontaneous fluctuations of birefringence in glasses doped with rare-earth (RE) ions. The fluctuations were observed in Nd$^{3+}$- and Yb$^{3+}$-doped glasses as polarization noise of the laser beam…