Resonant rayleigh scattering from bilayer quantum Hall phases

We observe resonant Rayleigh scattering of light from quantum Hall bilayers at Landau level filling factor nu = 1. The effect arises below 1 Kelvin when electrons are in the incompressible quantum Hall phase with strong interlayer correlations. Marked changes in the Rayleigh scattering signal in response to application of an in-plane magnetic field indicate that the unexpected temperature dependence is linked to formation of a nonuniform electron fluid close to the phase transition towards the compressible state. These results demonstrate a new realm of study in which resonant Rayleigh scattering methods probe quantum phases of electrons in semiconductor heterostructures.     

Electron-phonon scattering in asymmetric semiconductor quantum-well structures

We calculate scattering rates of intrasubband and intersubband electronic transitions in asymmetric single quantum wells (QW's) and step QW's due to interface phonons, confined bulk-like LO phonons, and half-space LO phonons. The relative importance of the different phonon modes is analyzed. The results show that the electron-phonon scattering rates have intimate relation to the QW parameters.     

Coherent rayleigh scattering

The spectrum of coherent scattering induced by electrostriction in gases has been analyzed in the previously unexplored, free-molecule limit by solving Boltzmann's equation with a periodic force due to the optical fields. Calculated and measured spectra of several gases at rarefied conditions are nearly Gaussian with widths approximately 10% wider than the spontaneous Rayleigh widths. Our results are the first spectrally resolved measurements of coherent Rayleigh scattering in the free-molecule limit, where the hydrodynamic analysis of stimulated Rayleigh-Brillouin scattering does not apply.     

Resonant elastic scattering of light from single quantum wells in semiconductor multilayers

A theory is developed for steady-state elastic scattering of light via quasi-2D excitons from a quantum well (QW) whose interfaces are randomly rough. The study is mainly focused on the angle dependences of radiation giving direct information about static disorder responsible for the elastic scattering. A nonlocal excitonic susceptibility is expressed in terms of random profile functions of QW interfaces. Treated is elastic scattering of light from a disordered QW in the following actual dielectric environments: (i) a uniform background, (ii) a Fabry–Perot film with rough boundaries, and (iii) a semiconductor microcavity. The cross-sections are derived analytically for scattering of linearly polarized light to the lowest (Born's) approximation with arbitrary roughness statistics. The spectral and angle dependencies of scattering intensity are analyzed numerically in the absolute-value scale with Gaussian correlation of interface roughness. The probability 10⁻² was found for the exciton-mediated scattering of a photon from a QW interface roughness whose root-mean-square height is on the level of 2×10⁻¹ nm. This probability is shown to exceed by two orders of magnitude that is typical of resonant scattering from either a single semiconductor surface or rough boundaries of a semiconductor Fabry–Perot film containing the QW. The scattering spectrum of a QW placed in a microcavity is predicted to have a doublet structure whose components are associated with the cavity exciton–polaritons.     

Spectral narrowing in coherent rayleigh scattering

Spectral narrowing of the coherent Rayleigh scattering line shape in a room temperature CO(2) gas (2.5 x 10(23) m(-3)) with intense fields in the 10(15) W m(-2) range is observed. The line shape saturates to a width of approximately half that observed at low pump intensities and indicates a transition from scattering primarily from untrapped molecules to that from both trapped and untrapped molecules that are localized by the deep (60 K) optical potentials produced by the pump beams. At higher densities (5 x 10(24) m(-3)), collisions between the trapped and untrapped molecules broaden the spectral profile.     

Resonant inelastic X-ray scattering of tantalum double perovskite structures

In this paper, we investigated the electronic structures and defect states of SrLaMgTaO₆ (SLMTO) double perovskite structures by using resonant inelastic x-ray scattering. Recently, Eu³⁺ doped SLMTO red phosphors have been vigorously investigated due to their higher red emission efficiency compared to commercial white light emitting diodes (W-LED). However, a comprehensive understanding on the electronic structures and defect states of host SLMTO compounds, which are specifically related to the W-LED and photoluminescence (PL), is far from complete. Here, we found that the PL spectra of SLMTO powder compounds sintered at a higher temperature, 1400 °C, were weaker in the blue emission regions (at around 400 nm) and became enhanced in near infrared (NIR) regions compared to those sintered at 1200 °C. To elucidate the difference of the PL spectra, we performed resonant inelastic x-ray spectroscopy (RIXS) at Ta L-edge. Our RIXS result implies that the microscopic origin of different PL spectra is not relevant to the Ta-related defects and oxygen vacancies.     

Resonant raman scattering at the E1 energy gap of semiconductor crystals

We present a discussion of resonant Raman scattering by optical phonons at the E₁ energy gap of group IV and groups III–V compound semiconductor crystals (e.g., Ge and InSb). For allowed scattering by TO and LO phonons, the q-dependent “double resonant” two-band calculation of the Raman tensor may display destructive interference effects when the intermediate electron-hole pairs are uncorrelated. We also discuss the Franz-Keldysh mechanism of resonant electric field induced Raman scattering by LO phonons. The double resonance terms due to this mechanism will, for large electric fields, broaden and have its largest resonance enhancement at the energy gap.     

The spin dependence of rayleigh scattering

The scattering amplitude for the scattering of circularly polarized KeV photons by a magnetized 3d transition metal is derived. In addition to the well-known form factor approximation a spin dependent term is found. It is smaller by a factor ω/mc ² (ω being the photon energy) and proportional to the spin magnetic form factor. Results for the degree of polarization are too small to explain recent experiments.     

Resonant structures in24Mg+28Si elastic and inelastic scattering

The data on the excitation functions of²⁴Mg+²⁸Si elastic and inelastic (2⁺ ?0⁺, 2⁺ ?2⁺, 4⁺ ?0⁺ and 4⁺ ?2⁺) scattering fromE _c.m.=48.97 to 57.21 MeV have been subjected to a statistical analysis consisting of the calculations of deviation function, cross-correlation function, summed excitation function, cross-channel correlation coefficients, coherence widths, and the distribution of cross sections. Based on the outcome of the analysis resonant structures atE _c.m.=49.23, 50.02, 50.51, 52.10, 52.53, 53.27 and 54.14 MeV have been confirmed and three new structures of the same nature have been identified atE _c.m.=51.42, 54.88 and 55.60 MeV.     

Resonant Raman scattering from CdTe/ZnTe self-assembled quantum dot structures

We report resonant Raman scattering results of CdTe/ZnTe self-assembled quantum dot (QD) structures. Photoluminescence spectra reveal that the band gap energies of the CdTe QDs decrease with the increase of CdTe thickness from 2.0 to 3.5 monolayers, which indicates that the size of the QDs increases. When the CdTe/ZnTe QD structures are excited by non-resonant excitation, a longitudinal optical (LO) phonon response from the ZnTe barrier material is observed at 206 cm⁻¹. In contrast, when the CdTe/ZnTe QD structures are resonantly excited near the band gap energy of the QDs, additional phonon modes emerge at 167 and 200 cm⁻¹, while the ZnTe LO phonon response completely disappears. The 167 cm⁻¹ mode corresponds to the LO phonon of the CdTe QDs. A spatially resolved Raman scattering from the cleaved edge of the QD sample reveals that the 200 cm⁻¹ mode is strongly localized at the interface between the CdTe QDs and ZnTe cap layer. This phonon mode is attributed to the interface optical (IO) phonon. The analytically calculated value of the IO phonon energy using a dielectric continuum approach, assuming a spherical dot boundary, agrees well with the experimental value.     

Resonant impurity bands in semiconductor superlattices

It is shown that the confined impurity state of a semiconductor quantum well develops into an excited impurity band in the case of a superlattice. This is studied by following theoretically the transition from a single to a multiple quantum well or superlattice by exactly diagonalizing the three-dimensional Hamiltonian for a quantum well system with random impurities. Intersubband absorption experiments, which can be nearly perfectly reproduced by the theory, corroborate this interpretation, which also requires reinterpretation of previous data.     

Resonant Raman scattering in germanium

We have studied the spectral dependence of the first order Raman scattering cross section of Ge at room and liquid nitrogen temperatures in the energy region containing the E₁ and E₁ + Δ₁ optical gaps. This region was covered by a fine mesh of points obtained from the discrete lines of three gas lasers and a cw continuously tunable dye laser. Only one resonant peak was observed, as opposed to the two peaks that characterise the absorption and reflection spectra in this region. The shape of this resonance peak can be explained as due to the changes in the electronic polarizability produced by phonon-induced wave function mixing of the spin-orbit split Λ valence band doublet. The observed temperature shift in the resonant energy is much smaller than the one predicted from the known shifts of the optical gaps with temperature. Furthermore the resonant peak at room temperature appears shifted to higher energies when compared with the theoretical peak calculated from the room temperature optical constants. The resonant Raman peak appears to shift with increasing temperature by the full thermal expansion effect plus only a fraction of the electron-phonon interaction shift seen in the optical constants.     

Measurement of thomson and rayleigh scattering in a preionizationZ-pinch

A 90° scattering experiment with a preionizationZ-pinch is described. The first part describes conventional measurements of the electron temperature and density (Thomson scattering). In the second part of the experiment Rayleigh scattering from excited hydrogen atoms was observed during very early phases of the discharge. This observation is possible because the Rayleigh scattering cross section of hydrogen atoms in the second and third quantum states is very large because of the small difference in the energy of the photons ofH _α (6563 Å) and the light of a ruby laser (6943 Å). Spectral resolution of this part of the scattered light yields a minimum value for the ion temperature.     

Resonant scattering of solitons

We study the scattering of solitons in the nonlinear Schr?dinger equation on local inhomogeneities which may give rise to resonant transmission and reflection. In both cases, we derive resonance conditions for the soliton's velocity. The analytical predictions are tested numerically in regimes characterized by various time scales. Special attention is paid to intermode interactions and their effect on coherence, decoherence, and dephasing of plane-wave modes which build up the soliton.     

Resonant tunnelling lifetime in the semiconductor superlattice

The fundamental physics of the resonant tunnelling lifetime (RTL) in superlattices have been theoretically studied. The modelling of this RTL is based on a relationship between the resonant tunnelling and the half-width at half-maximum of the transmission peak. The lifetime of resonant states and the current density accompany the resonant tunnelling change as a function of mole fraction of the barrier layer, well width and barrier width. The energies and the lifetime of the electrons at the resonant states are correlated with the band structure of the superlattices. It is seen that the variation in RTL with resonance energy has a special minima, and that these minima occur around the centre of the allowed bands.     

Superfluorescent rayleigh scattering from suspensions of dielectric particles

We demonstrate that superfluorescent scattering of light can occur when laser light is incident on a collection of dielectric Rayleigh particles suspended in a viscous medium. Using a linear stability analysis, an expression for the spatiotemporal evolution of the scattered (probe) field is derived. An approximate condition for the progression of the interaction into the nonlinear regime is deduced and it is shown that, in the nonlinear regime, the scattered field intensity shows the characteristic quadratic dependence on particle density expected from a superfluorescent or superradiant process, once the effects of pump depletion are accounted for.