Search results for " density of states"

Generalized bloch equations for optical interactions in confined geometries

2005

By combining the field-susceptibility technique with the optical Bloch equations, a general formalism is developed for the investigation of molecular photophysical phenomena triggered by nanometer scale optical fields in the presence of complex environments. This formalism illustrate the influence of the illumination regime on the fluorescence signal emitted by a single molecule in a complex environment. In the saturated case, this signal is proportional to the optical local density of states, while it is proportional to the near-field intensity in the non-saturated case. (C) 2005 Elsevier B.V. All rights reserved.

Reply to “Comment to ‘Dynamics of supercooled confined water measured by deep inelastic neutron scattering’ by Y. Finkelstein and R. Moreh”

2019

We reply to the comment [Front. Phys. 14(5), 53605 (2019)] by Y. Finkelstein and R. Moreh on our article Front. Phys. 13(1), 138205 (2018). We agree with some of their criticisms about our calculation of the temperature effect on the kinetic energy of hydrogen atoms of supercooled confined water; we also agree with their statement that, in view of the current sensitivity of the technique, possible effects of the liquid-liquid water transition are hardly detected with deep inelastic neutron scattering (DINS). However, we disagree with their use of the translational mass ratio of a single water molecule and, in general, with their underestimation of collective effects.

First-principles simulations of the electronic density of states for superionic Ag2CdI4 crystals

2011

Abstract Energy band dispersion calculations have been performed for Ag 2 CdI 4 superionic within a framework of local density approximation (Perdew–Zunger parameterization) exploiting the first-principles CASTEP computer code. The ab-initio electronic structure simulations were performed for both ( I 4 and I 42 m ) types of e -Ag 2 CdI 4 crystalline structures. Principal optical functions as well as the density of electronic states in the spectral range of inter-band optical transitions (2.5 eV–20 eV) were determined. Theoretically calculated absorption coefficients derived from the obtained band structure are compared with appropriate experimental data.

Tuning the Pseudospin Polarization of Graphene by a Pseudomagnetic Field.

2016

One of the intriguing characteristics of honeycomb lattices is the appearance of a pseudo-magnetic field as a result of mechanical deformation. In the case of graphene, the Landau quantization resulting from this pseudo-magnetic field has been measured using scanning tunneling microscopy. Here we show that a signature of the pseudo-magnetic field is a local sublattice symmetry breaking observable as a redistribution of the local density of states. This can be interpreted as a polarization of graphene's pseudospin due to a strain induced pseudo-magnetic field, in analogy to the alignment of a real spin in a magnetic field. We reveal this sublattice symmetry breaking by tunably straining grap…

Odd triplet superconductivity induced by the moving condensate

2020

It has been commonly accepted that magnetic field suppresses superconductivity by inducing the ordered motion of Cooper pairs. We demonstrate that magnetic field can instead provide a generation of superconducting correlations by inducing the motion of superconducting condensate. This effect arises in superconductor/ferromagnet heterostructures in the presence of Rashba spin-orbital coupling. We predict the odd-frequency spin-triplet superconducting correlations called the Berezinskii order to be switched on at large distances from the superconductor/ferromagnet interface by the application of a magnetic field. This is shown to result in the unusual behaviour of Josephson effect and local d…

Electronic and optical properties of CeO 2 from first principles calculations

2016

International audience; First-principles calculations of the electronic structure of CeO2 nanoparticles (NPs) were performed to investigate published experimental data obtained by different spectroscopies. The main features of the valence and conduction bands have been analyzed from the total and partial density of states. Several functionals were applied to interpret and quantify the optical properties, including the dielectric function, extinction coefficient and refractive index. It is found that the on-site hybrid functional B3PW91 modelled most suitably the band gap region of CeO2 NPs and consequently gave a more accurate band gap value. It also agreed very well with the experimental v…

Theoretical principles of near-field optical microscopies and spectroscopies

2000

International audience; This paper deals with the principles of detection of optical signals near a surface in a manner permitting the mapping of the distribution of the fields close to various kinds of illuminated samples. We begin with a discussion of the main physical properties of the optical fields near a surface in the absence of any probe tip. This mainly concerns phenomena involving evanescent waves for which the local decay lengths are governed not only by the sizes but also by the intrinsic properties of the surface structures. The interpretation of the detection process is reviewed on the basis of a discussion about the possibility of establishing direct comparisons between exper…

Characterization of defect density states in MoOx for c-Si solar cell applications

Layers of MoOx have been deposited by thermal evaporation followed by post-deposition annealing (PDA). The density of states (DOS) distributions of the MoOx films were extracted deconvoluting the absorption spectra, measured by a phothermal deflection spectroscopy setup, including the small polaron contribution. Results revealed a sub-band defect distribution centered 1.1 eV below the conduction band; the amplitude of this distribution was found to increase with PDA temperature and film thickness.

Effect of physical aging on the low-frequency vibrational density of states of a glassy polymer

2003

The effects of the physical aging on the vibrational density of states (VDOS) of a polymeric glass is studied. The VDOS of a poly(methyl methacrylate) glass at low-energy (<15 meV), was determined from inelastic neutron scattering at low-temperature for two different physical thermodynamical states. One sample was annealed during a long time at temperature lower than Tg, and another was quenched from a temperature higher than Tg. It was found that the VDOS around the boson peak, relatively to the one at higher energy, decreases with the annealing at lower temperature than Tg, i.e., with the physical aging.

Supercooled Water Confined in a Silica Xerogel: Temperature and Pressure Dependence of Boson Peak and of Mean Square Displacements

2013

A silica xerogel can be obtained from an alcoxide precursor (TMOS, tetramethylortosilcate) via the sol-gel method: TMOS hydrolysis and subsequent polycondensation yields a solid, disordered, porous SiO2 matrix (average pore dimensions ~20Å). Inside the pores water is trapped and the hydration level h=gr[H2O]/gr[SiO2] can be easily controlled. The presence and temperature dependence of the boson peak (BP) in xerogel confined supercooled water was studied with inelastic neutron scattering (spectrometer IN6 at ILL, Grenoble) in xerogel samples having h=0.4 and h=0.2. After careful subtraction of the contributions arising from the matrix and from quasi-elastic scattering, the BP contribution wa…