Brillouin zone

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

Microscopic theory of intervalley scattering in GaAs : K dependence of deformation potentials and scattering rates

Abstract: The ‘‘rigid‐pseudoion’’ model is applied to intervalley scattering processes in GaAs The intervalley deformation potentials (IDPs) that we obtain at high‐symmetry points are in good agreement with previous calculations We find that the IDPs show a strong dependence on the wave vector of the intervalley phonon, therefore a numerical integration over the Brillouin zone (eg, with the tetrahedron method) is necessary to obtain realistic scattering rates that can be compared with those obtained from experiments We calculate the lifetimes of electrons at the L and X valleys as a function of temperature (L: 22±05 ps; X: 130±20 fs at room temperature) and discuss our results in comparison with recent ultrafast laser experiments and Monte Carlo simulations Finally, the IDPs show an anisotropy that might be important when simulating electrical transport in hot‐electron devices

Electrical conductivity of metallic Si:B near the metal-insulator transition

Abstract: The conductivity has been measured between 55 mK and 4.2 K in zero field and in magnetic fields up to 7.5 T of a series of uncompensated {ital p}-type Si:B samples with dopant concentrations near the critical concentration for the metal-insulator transition. Acceptor wave functions, which are derived in silicon from the degenerate light- and heavy-hole {ital J}=3/2 valence-band maxima at {ital k}=0 and a spin-orbit-split {ital J}=1/2 band, are quite different from donor wave functions associated with the six degenerate conduction-band minima at different equivalent points in the Brillouin zone. Despite this, the conductivity of Si:B is found to be quite similar in many ways to that of Si:P. The critical conductivity exponent for Si:B is close to 1/2 as in Si:P and Si:As, rather than having the expected value of 1. The correction to the zero-temperature conductivity arising from electron-electron interactions is comparable in size, and the temperature dependence of the conductivity in various fixed magnetic fields is also found to be quite similar. For the range of dopant concentrations and experimental parameters of these investigations, the only important experimental difference between the two materials is the sign and size of the magnetoresistance. In contrast with Si:P, whichmore » has both positive and negative components, the magnetoresistance of Si:B is positive for all temperatures and magnetic fields studied. We attribute this to the strong spin-orbit scattering in {ital p}-type silicon associated with the degenerate valence bands.« less

Double resonance Raman modes in monolayer and few-layer MoTe2

Abstract: We study the second-order Raman process of mono- and few-layer ${\mathrm{MoTe}}_{2}$, by combining ab initio density functional perturbation calculations with experimental Raman spectroscopy using 532, 633, and 785 nm excitation lasers. The calculated electronic band structure and the density of states show that the resonance Raman process occurs at the $M$ point in the Brillouin zone, where a strong optical absorption occurs due to a logarithmic Van Hove singularity of the electronic density of states. The double resonance Raman process with intervalley electron-phonon coupling connects two of the three inequivalent $M$ points in the Brillouin zone, giving rise to second-order Raman peaks due to the $M$-point phonons. The calculated vibrational frequencies of the second-order Raman spectra agree with the observed laser-energy-dependent Raman shifts in the experiment.

Method for measuring volumetric changes of object

Abstract: Under a known pressure is externally applied to a reference member to which an optical fiber is fixed, test light is allowed to enter the optical fiber, and at least one of a reference Brillouin measurement for determining a reference Brillouin frequency shift amount based on the Brillouin scattering phenomenon, and a reference Rayleigh measurement for determining a reference Rayleigh frequency shift amount based on the Rayleigh scattering phenomenon is performed. A Brillouin measurement coefficient or a Rayleigh measurement coefficient is determined from these calculation results. An optical fiber is fixed to a sample member, the volumetric change of which is unknown, and the same sample Brillouin measurement or sample Rayleigh measurement is performed to determine the frequency shift amount. The volumetric change of the sample member is determined from the sample Brillouin or the sample Rayleigh frequency shift amount, and from the Brillouin or the Rayleigh measurement coefficient.