Brillouin zone

About: Brillouin zone is a research topic. Over the lifetime, 13849 publications have been published within this topic receiving 383077 citations.

Low-Field de Haas-van Alphen Effect in Zinc

Abstract: A study of the low-field de Haas-van Alphen effect in zinc, employing automatic recording of the variation of the torque as a function of the reciprocal of the applied magnetic field, has revealed six sets of periods. These periods are assigned in a consistent manner to portions of the free-electron (single orthogonalized planewave) model of the Fermi surface. Cyclotron masses associated with the three larger sets of observed periods are found to agree well with the theoretical estimates. Evidence is obtained for the presence of a spin-orbit energy gap across the hexagonal face of the first Brillouin zone near the corners. Thus, the validity of the single Brillouin-zone construction is demonstrated for zinc.

Phononic filter effect of rattling phonons in the thermoelectric clathrate Ba8Ge40+xNi6-x.

Abstract: One of the key requirements for good thermoelectric materials is a low lattice thermal conductivity. Here we present a combined neutron scattering and theoretical investigation of the lattice dynamics in the type I clathrate system Ba-Ge-Ni, which fulfills this requirement. We observe a strong hybridization between phonons of the Ba guest atoms and acoustic phonons of the Ge-Ni host structure over a wide region of the Brillouin zone, which is in contrast with the frequently adopted picture of isolated Ba atoms in Ge-Ni host cages. It occurs without a strong decrease of the acoustic phonon lifetime, which contradicts the usual assumption of strong anharmonic phonon--phonon scattering processes. Within the framework of ab initio density-functional theory calculations we interpret these hybridizations as a series of anticrossings which act as a low-pass filter, preventing the propagation of acoustic phonons. To highlight the effect of such a phononic low-pass filter on the thermal transport, we compute the contribution of acoustic phonons to the thermal conductivity of Ba${}_{8}$Ge${}_{40}$Ni${}_{6}$ and compare it to those of pure Ge and a Ge${}_{46}$ empty-cage model system.

Correlation-based distributed measurement of a dynamic grating spectrum generated in stimulated Brillouin scattering in a polarization-maintaining optical fiber

Abstract: We study the principle of correlation-based distributed generation and readout of dynamic grating spectrum generated in stimulated Brillouin scattering in a polarization-maintaining optical fiber. The experimental validation is demonstrated by applying synchronous sinusoidal frequency modulations to two orthogonally polarized laser sources that serve as the Brillouin pump-probe light and readout light of the dynamic grating, respectively. Temperature-induced opposite changes in the Brillouin frequency shift and in the birefringence-determined optical frequency deviation are clearly observed with 1.2 m spatial resolution and a 110 m measurement range.

Flat amplitude multiwavelength Brillouin-Raman comb fiber laser in Rayleigh-scattering-enhanced linear cavity.

Abstract: We investigate the amplitude flatness of Rayleigh-assisted Brillouin-Raman comb laser in a linear cavity in which feedbacks are formed by high-reflectivity mirror. The optimization of Brillouin pump power and wavelength is very crucial in order to obtain a uniform power level between Stokes lines. The Brillouin pump must have a relatively large power and its wavelength must be located closer to the Raman peak gain region. The flat-amplitude bandwidth is also determined by the choice of Raman pump wavelengths. A flat-amplitude bandwidth of 30.7 nm from 1527.32 to 1558.02 nm is measured when Raman pump wavelengths are set to 1435 and 1450 nm. 357 uniform Brillouin Stokes lines with 0.086 nm spacing are generated across the wavelength range. The average signal-to-noise ratio of 17 dB is obtained for all the Brillouin Stokes lines.