Search results for "Solid"
showing 10 items of 3575 documents
Density-near-zero using the acoustically induced transparency of a Fano acoustic resonator
2016
International audience; We report experimental results of near-zero mass density involving an acoustic metamaterial supporting Fano resonance. For this, we designed and fabricated an acoustic resonator with two closely coupled modes and measured its transmission properties. Our study reveals that the phenomenon of acoustically induced transparency is accompanied by an effect of near-zero density. Indeed, the dynamic effective parameters obtained from experimental data show the presence of a frequency band where the effective mass density is close to zero, with high transmission levels reaching 0.7. Furthermore, we demonstrate that such effective parameters lead to wave guiding in a 90-degre…
Paramagnetic-diamagnetic interplay in quantum dots for non-zero temperatures
2000
In the usual Fock-and Darwin-formalism with parabolic potential characterized by the confining energy $\eps_o := \hbar\omega_o= 3.37$ meV, but including explicitly also the Zeeman coupling between spin and magnetic field, we study the combined orbital and spin magnetic properties of quantum dots in a two-dimensional electron gas with parameters for GaAs, for N =1 and N >> 1 electrons on the dot. For N=1 the magnetization M(T,B) consists of a paramagnetic spin contribution and a diamagnetic orbital contribution, which dominate in a non-trivial way at low temperature and fields rsp. high temperature and fields. For N >> 1, where orbital and spin effects are intrinsically coupled in a subtle w…
Isotropic Chiral Acoustic Phonons in 3D Quasicrystalline Metamaterials.
2020
International audience; The elastic properties of three-dimensional (3D) crystalline mechanical metamaterials, unlike those of amorphous structures, are generally strongly anisotropic—even in the long-wavelength limit and for highly symmetric crystals. Aiming at isotropic linear elastic wave propagation, we therefore study 3D periodic approximants of 3D icosahedral quasicrystalline mechanical metamaterials consisting of uniaxial chiral metarods. Considering the increasing order of the approximants, we approach nearly isotropic effective speeds of sound and isotropic acoustical activity. The latter is directly connected to circularly polarized 3D metamaterial chiral acoustic phonons—for all …
Elastodynamic behavior of mechanical cloaks designed by direct lattice transformations
2020
International audience; <h2 class="section-title u-h3 u-margin-l-top u-margin-xs-bottom" style="box-sizing: border-box; padding: 0px; font-weight: 400 !important; color: #505050; font-size: 1.2rem !important; line-height: 1.333 !important; font-family: NexusSerif, Georgia, 'Times New Roman', Times, STIXGeneral, 'Cambria Math', 'Lucida Sans Unicode', 'Microsoft Sans Serif', 'Segoe UI Symbol', 'Arial Unicode MS', serif; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-styl…
Relationship between scanning near-field optical images and local density of photonic states
2001
From numerical calculations based on Green's dyadic formalism, we show that a scanning near-field optical microscope (SNOM) working with a point-like illuminating probe delivers images that contain features directly related to the local density of photonic states (LDOS). More precisely, an unambiguous identification of the partial LDOSs (x, y or z polarized) can be made in the SNOM images when the solid angle of detection reaches 2π sr.
Ultra-broadband terahertz time domain spectroscopy by Solid State Biased Coherent Detection
2017
The spectral fingerprint of ibuprofen within the THz frequency window has been retrieved through an ultra-broadband THz Time Domain Spectrometry set-up. The latter implements the Solid State Biased Coherent Detection scheme, based on a compact CMOS-compatible integrated device. Such a technique shows unprecedented advantages in term of bandwidth (greater than 10 THz) over other solid state methods like electro-optic sampling.
Finite amplitude method applied to giant dipole resonance in heavy rare-earth nuclei
2015
Background: The quasiparticle random phase approximation (QRPA), within the framework of the nuclear density functional theory (DFT), has been a standard tool to access the collective excitations of the atomic nuclei. Recently, finite amplitude method (FAM) has been developed, in order to perform the QRPA calculations efficiently without any truncation on the two-quasiparticle model space. Purpose: We discuss the nuclear giant dipole resonance (GDR) in heavy rare-earth isotopes, for which the conventional matrix diagonalization of the QRPA is numerically demanding. A role of the Thomas-Reiche-Kuhn (TRK) sum rule enhancement factor, connected to the isovector effective mass, is also investig…
Sound attenuation and anharmonic damping in solids with correlated disorder
2010
We study via self-consistent Born approximation a model for sound waves in a disordered environment, in which the local fluctuations of the shear modulus G are spatially correlated with a certain correlation length The theory predicts an enhancement of the density of states over Debye's omega(2) law (boson peak) whose intensity increases for increasing correlation length, and whose frequency position is shifted downwards as lg. Moreover, the predicted disorder-induced sound attenuation coefficient r(k) obeys a universal scaling law F(k) = f (ke) for a given variance of G. Finally, the inclusion of the lowest-order contribution to the anharmonic sound damping into the theory allows us to rec…
Photoionization of Polarized Atoms Applications to Free Atoms and Ferromagnets
1996
Discussion of connections between different phenomena observed in seemingly different situations usually helps to better understanding of the physics of underlying processes. Some time ago Farago1 discussed analogies and contrasts between light polarization and electron spin polarization. He showed that though in both cases the same Stokes vector formalism2 can be applied, the analogies between them have rather limited validity. We will discuss here the applicability of equations derived for the description of photoionization of free polarized atoms3,4 to photoemission from ferromagnets5,6. We show that qualitative features of photoemission from core levels of ferromagnets are correctly rep…
Detuning-induced robustness of a three-state Landau-Zener model against dissipation
2019
A three-state system subjected to a time-dependent Hamiltonian whose bare energies undergo one or more crossings, depending on the relevant parameters, is considered, also taking into account the role of dissipation in the adiabatic following of the Hamiltonian eigenstates. Depending on the fact that the bare energies are equidistant or not, the relevant population transfer turns out to be very sensitive to the environmental interaction or relatively robust. The physical mechanisms on the basis of this behavior are discussed in detail.