Investiation of the effects of a quantum dot crystal geometry on its brillouin spectrum
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Double-Edge Molecular Technique for Doppler Lidar Wind Measurement
The double-edge lidar technique for measuring the wind using molecular backscatter is described. Two high spectral resolution edge filters are located in the wings of the Rayleigh-Brillouin profile. This doubles the signal change per unit Doppler shift, the sensitivity, and gives nearly a factor of two improvement in measurement accuracy. The use of a crossover region is described where the sensitivity of a molecular and aerosol-based measurement are equal. This desensitizes the molecular measurement to the effects of aerosol scattering over a frequency range of +/- 100 m/s. We give methods for correcting for short-term frequency jitter and drift using a laser reference frequency measurement and methods for long-term frequency correction using a servo control system. The effects of Rayleigh-Brillouin scattering on the measurement are shown to be significant and are included in the analysis. Simulations for a conical scanning satellite-based lidar at 355 nm show an accuracy of 2-3 m/s for altitudes of 2 to 15 km for a 1 km vertical resolution, a satellite altitude of 400 km and a 200 km x 200 km spatial resolution. Results of ground based wind measurements are presented.
Flesia, Cristina↗
Nondegenerate surface pair density wave in the kagome superconductor CsV 3 Sb 5 : Application to vestigial orders
On the Sb layer of the kagome superconductor CsV 3 Sb 5 , pair density wave states have been observed. When the high-temperature charge orderings are treated as static backgrounds, these pair density wave (PDW) states exhibit the same wave vector in the effective two-dimensional Brillouin zone. Interestingly, these PDW states break the same symmetry on the surface. Considering the presence of this nondegenerate PDW, we investigate the implications for the possible existence of a vestigial charge-4 e phase with a nonzero center-of-mass momentum. To distinguish between different vestigial phases, we propose scanning tunneling microscopy experiments. Here we aim to provide insights into the nature of the vestigial phases and their distinct characteristics in CsV 3 Sb 5 . This research sheds light on the interplay between PDW states, charge orderings, and superconductivity of the kagome superconductor.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Direct evidence for majority carrier locations in the Brillouin zone of graphite
Thermoelectric power and Hall effect quantum resonances in graphite for locating majority carrier electron and hole Fermi Surfaces in Brillouin zone
Woollam, J. A.↗
Self-focusing of pseudo-nondiffracting laser beams with circular symmetry in collisional plasma under two ramp density profiles
The self-focusing of zeroth-order Bessel–Gaussian beams through plasma under exponential and tangential ramp density profiles is investigated theoretically by using Wentzel–Kramers–Brillouin approximation. To examine the effect of plasma density ramp on self-focusing of the studied beams, the evolution of beam-width parameter with normalized propagation distance is reported for diverse laser beams and plasma parameters. The results reveal that stronger self-focusing is obtained with exponential ramp density profile as compared to the tangential density ramp one.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Electronic structure of p -type transparent conducting oxide CuAlO 2
We report copper-based delafossite oxides are excellent candidates for the p-type transparent conducting oxide (TCO), which is essential in realizing transparent semiconductor applications. Using angle-resolved photoemission spectroscopy (ARPES), we report the low-energy electronic structure of CuAlO 2 . We found that the band structure near the valence band top is characterized by hole bands with their maxima along the Brillouin zone boundary. Furthermore, the effective masses along the Γ–M and Γ–K directions were found to be (0.6 ± 0.1) m0 and (0.9 ± 0.1) m 0 , respectively, which impose an important benchmark against the existing band calculations.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Electronic spectrum of crystalline antimony.
Energy levels and interband oscillator strengths of antimony calculated in Brillouin zone by pseudopotential method, predicting polarization effects and spin-orbit splittings
BRILLOUIN ZONE↗
Study of mid IR fiber transmission and mode patterns under laser induced stimulated Brillouin scattering
Mid IR fiber transmission and exit radiation mode patterns at various incident CO2 laser power levels appear to be effective diagnostic tools for monitoring laser induced stimulated Brillouin scattering in various mid IR fibers. Such processes are deemed to be essential mechanisms for fiber-optic amplifiers and switches as potential replacements of current repeaters and bistable devices.
Yu, C.↗
The competing effects of wave amplitude and collisions on multi-ion species suppression of stimulated Brillouin scattering in inertial confinement fusion Hohlraums
Reduction in stimulated Brillouin scattering (SBS) from National Ignition Facility Hohlraums has been predicted through the use of multi-ion species materials on Hohlraum walls. This approach to controlling SBS is based upon introducing a lighter ion species to the heavier ion species Hohlraum wall in order to greatly increase the ion Landau damping of ion acoustic waves (IAWs). In a collisionless plasma, if the IAWs driven by SBS reach sufficient amplitudes, this increased damping is reduced or even eliminated by ion trapping in the IAWs. Here, the nonlinear behavior of IAWs is simulated with a multi-ion species Vlasov code, including interspecies ion–ion collisions, self-collisions, and electron–ion pitch-angle collisions. The effect of collisions on the trapping of ions and electrons in a large-amplitude IAW is studied in a regime of relevance to current Inertial Confinement Fusion experiments. Our simulations show that collisions can scatter trapped particles out of resonance with the IAW, suppressing trapping and helping to maintain an effective Landau damping of the IAW. The IAW amplitude required to trap particles in the presence of strong collisions is estimated analytically. These estimates are tested for strongly damped IAWs in tantalum oxide and pure helium plasmas. Here our simulations show that, above a threshold amplitude, the damping is reduced by an amount inversely proportional to the wave amplitude. Thus, the success of controlling SBS using a multispecies plasma may depend sensitively on laser power and pulse length.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Research on stability and uniformity of multi-wavelength Brillouin-erbium fiber laser based on FWM
In this paper, we experimentally and theoretically investigate the stability and uniformity of multi-wavelength Brillouin-erbium fiber laser based on four-wave mixing (FWM). Multi-wavelength generation is limited by cross-gain saturation between different wavelengths from homogeneous broadening of erbium-doped fiber. Modeling coupled-mode equation for FWM and analyzing the influence of FWM on multi-wavelength generation. 16 orders Brillouin Stokes (BS) waves with a wavelength spacing of 0.084 nm are obtained experimentally within a 3 dB bandwidth by the FWM effect in a 100 m highly nonlinear fiber (HNLF), power distribution of each laser is uniform and peak power fluctuation is less than 1.184 dB within a 10 dB bandwidth, the outputs exhibit good time stability and uniformity. Compared with the same configuration, the laser without HNLF has only 9 orders stable BS waves within 3 dB bandwidth, and high-order Stokes wave shows significant waveform jitter and power fluctuation.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Three-dimensional higher-order saddle-point-induced flatbands in Co-based kagome metals
The saddle point (Van Hove singularity) exhibits a divergent density of states in two-dimensional systems, leading to fascinating phenomena such as strong correlations and unconventional superconductivity, yet it is seldom observed in three-dimensional (3D) systems. In this work we find two types of 3D higher-order saddle points (HOSPs) in emerging 3D kagome metals YbCo 6 Ge 6 and MgCo 6 Ge 6 . Both HOSPs exhibit a singularity in their density of states, which is significantly enhanced compared to the ordinary saddle point. The HOSP near the Fermi energy generates a flatband extending a large area in the Brillouin zone, potentially amplifying the correlation effect and fostering electronic instabilities. Two types of HOSPs exhibit distinct robustness upon element substitution and lattice distortions in these kagome compounds. Our work paves the way for engineering exotic band structures, such as saddle points and flatbands, and exploring interesting phenomena in Co-based kagome materials.
36 MATERIALS SCIENCE↗
Instability Increments of Stimulated Mandelshtam–Brillouin Scattering in a Bounded Region with Allowance for Collisions
The problem of Mandelstam–Brillouin scattering in the region bounded in the direction of pump wave propagation and infinite in the transverse direction is considered. Such situations can arise, for example, in plasma heating or diagnostic problems. Since the time of scattered radiation escape for the examined geometry upon scattering at a certain angle increases substantially, this effect compensates for a decrease in the nonlinear feedback coefficient upon oblique scattering and leads to instability development. Since the convective losses at scattering angles close to π/2 are small, collisional absorption of waves plays an important role in this case. The instability increments are calculated taking into account not only the convective losses, but also the collisional wave attenuation.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Inelastic scattering in planetary atmospheres. I - The Ring effect, without aerosols
The contribution of inelastic molecular scattering (Rayleigh-Brillouin and rotational Raman scattering) to the filling-in of Fraunhofer lines in the light of the blue sky is studied. Aerosol fluorescence is shown to be negligible, and aerosol scattering is ignored. The angular and polarization dependences of the filling-in detail for single scattering are discussed. An approximate treatment of multiple scattering, using a backward Monte Carlo technique, makes it possible to investigate the effects of the ground albedo. As the molecular scatterings alone produce more line-filling than is observed, it seems likely that aerosols dilute the effect by contributing unaltered sunlight to the observed spectra.
Kattawar, G. W.↗
Crossover from Kondo to Fermi-liquid behavior induced by high magnetic field in 1 T -VTe 2 single crystals
The magnetic and magnetotransport properties of metallic 1T -VTe 2 single crystals were investigated at temperatures from 1.3 to 300 K and in magnetic fields up to 35 T. Upon applying a high magnetic field, it is found that the electrical resistivity displays a crossover from the logarithmic divergence of the single-impurity Kondo effect to the Fermi liquid behavior at low temperatures. The Brillouin scale of the negative magnetoresistivity above the Kondo temperature T K = 12 K indicates that the Kondo features originate from intercalated V ions, with S = 1/2. Both magnetic susceptibility and the Hall effect show an anomaly around T K . By using the modified Hamann expression we successfully describe the temperature-dependent resistivity under various magnetic fields, which shows the characteristic peak below T K due to the splitting of the Kondo resonance.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Electron dynamics and energy conversion in O-type linear-beam devices.
A general nonlinear interaction theory is used to investigate the effects of transverse fields (i.e., radial circuit fields and radial space-charge fields) in traveling-wave amplifiers for a variety of beam-focusing conditions. Magnetic focusing fields which are periodic or tapered (increased) with distance along the device are considered in addition to uniform magnetic fields. Results are presented for Brillouin flow and near-Brillouin flow, and the minimum magnetic field strength required to effectively constrain the electron beam is determined as a function of the operating parameters for the various focusing systems. Confined flow is also examined for the uniform-field case in order to have a basis of comparison from which the effects of radial motion of the beam electrons can be determined. The results indicate the importance of transverse effects and further yield information on the stability of strongly modulated cylindrical electron beams.-
Detweiler, H. K.↗
Interaction effects in graphene in a weak magnetic field
A weak perpendicular magnetic field, B, breaks the chiral symmetry of each valley in the electron spectrum of graphene, preserving the overall chiral symmetry in the Brillouin zone. Here we explore the consequences of this symmetry breaking for the interaction effects in graphene. In particular, we demonstrate that the electron-electron interaction lifetime acquires an anomalous B dependence. Also, the ballistic zero-bias anomaly, δv(ω), where ω is the energy measured from the Fermi level, emerges at a weak B and has the form δv(B) ~ B 2 /ω 2 . Temperature dependence of the magnetic-field corrections to the thermodynamic characteristics of graphene is also anomalous. We discuss experimental manifestations of the effects predicted. The microscopic origin of the B-field sensitivity is an extra phase acquired by the electron wave function resulting from the chirality-induced pseudospin precession.
36 MATERIALS SCIENCE↗
Reflection of Alfven waves in the solar wind
We have revisited the problem of propagation of toroidal and linear Alfven waves formulated by Heinemann and Olbert (1980) to compare Wentzel-Kramers-Brillouin (WKB) and non-WKB waves and their effects on the solar wind. They considered two solar wind models and showed that reflection is important for Alfven waves with periods of the order of one day and longer and that non-WKB Alfven waves are no more effective in accelerating the solar wind than in WKB waves. There are several recently published papers that seem to indicate that Alfven waves with periods of the order of several minutes should be treated as non-WKB waves and that these non-WKB waves exert a stronger acceleration force than WKB waves. The purposse of this paper is to study the origin of these discrepancies by performing parametric studies of the behavior of the waves under a variety of different conditions. In addition, we want to investigate two problems that have not been addressed by Heinimann and Olbert, namely, calculate the efficieny of Alfven wave reflection by using the reflection coefficient and identfy the region of strongest wave reflection in different wind models. To achieve these goals, we investigate the influence of temperature, electron desity distribution, wind velocity, and magnetic field strength on te waves. The obtained results clearly demonstrate that Alfven wave reflection is strongly model dependent and that the strongest reflection can be expected in models with the base temperatures higher than 10(exp 6) K and with the base densities lower than 7 x 10(exp 7)/cu cm. In these models as well as in the models with lower temperatures and higher densities Alfven waves with periods as short as several minutes have negligible reflection so that they can be treated as WKB waves; however, for Alfven waves with periods of the order of one hour or longer reflection is significant, requiring a non-WKB treatment. We also show that non-WKB, linear Alfven waves are always less effective in accelerating the plasma than WKB Alfven waves. Finally, it is evident from our results that the region of strongest wave reflection is usually located at the base of the models and hence that interpretation of wave reflection based soley on the reflection coefficient can be misleading.
Krogulec, M.↗
Multi-parameter distributed fiber optic sensing using double-Brillouin peak fiber in Brillouin optical time domain analysis
In this paper, we demonstrate a multi-parameter fiber sensing system based on stimulated Brillouin scattering in a double-Brillouin peak specialty fiber with enhanced Brillouin gain response. The amplitude level of the second Brillouin gain peak, which originated from the higher-order acoustic modes, has been improved with an approximately similar amplitude level to the first Brillouin gain peak from the fundamental acoustic mode. Compared to other multi-Brillouin peak fibers presented in the literature, the proposed fiber significantly reduces the measured Brillouin frequency shift error, thus improving strain and temperature accuracies. By utilizing the sensitivity values of the strain and temperature associated with each Brillouin gain spectrum (BGS) peak, a successful discriminative measurement of strain and temperature is performed with an accuracy of ±13 μɛ, and ±0.5 °C, respectively. The proposed double-Brillouin peak fiber appears to be a possible alternative to other multi-BGS peak fibers, for instance, large effective area fiber and dispersion compensating fibers, which are inherently accompanied by large measurement errors due to the weak Brillouin gain values originating from the higher-order acoustic modes. The demonstrated results show different strain and temperature coefficients of 47 kHz/µɛ, 1.15 MHz/°C for peak 1 and 51 kHz/µɛ, 1.37 MHz/°C for peak 2. Moreover, the enhanced BGS peak gains having nearly the same amplitude levels enable the discriminative measurement of strain and temperature. Such fibers in Brillouin interrogation eliminate the need for complex monitoring setups and reduce measurement errors. We recommend that for long-distance natural gas pipeline monitoring, where discriminative strain and temperature measurement is crucial, the proposed double-Brillouin peak fiber can be highly beneficial.
47 OTHER INSTRUMENTATION↗