Topic
Brillouin zone
About: Brillouin zone is a research topic. Over the lifetime, 13849 publications have been published within this topic receiving 383077 citations.
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01 Dec 2010
TL;DR: The first demonstration of on-chip stimulated Brillouin scattering (SBS) is reported and the measured BrillouIn shift and line width are ∼7.7 GHz and 6 MHz in a 7 cm long chalcogenide waveguide.
Abstract: We report the first demonstration of on-chip stimulated Brillouin scattering (SBS) with low average power. The measured Brillouin shift and line width are ∼7.7 GHz and ∼6 MHz in a 7 cm long chalcogenide waveguide.
293 citations
TL;DR: Angle-resolved photoemission spectroscopy measurements in CoSi reveal the presence of unconventional chiral fermions near the Fermi level, with giant surface Ferm i arcs and one pair of well separated chiral nodes.
Abstract: Chirality—the geometric property of objects that do not coincide with their mirror image—is found in nature, for example, in molecules, crystals, galaxies and life forms. In quantum field theory, the chirality of a massless particle is defined by whether the directions of its spin and motion are parallel or antiparallel. Although massless chiral fermions—Weyl fermions—were predicted 90 years ago, their existence as fundamental particles has not been experimentally confirmed. However, their analogues have been observed as quasiparticles in condensed matter systems. In addition to Weyl fermions1–4, theorists have proposed a number of unconventional (that is, beyond the standard model) chiral fermions in condensed matter systems5–8, but direct experimental evidence of their existence is still lacking. Here, by using angle-resolved photoemission spectroscopy, we reveal two types of unconventional chiral fermion—spin-1 and charge-2 fermions—at the band-crossing points near the Fermi level in CoSi. The projections of these chiral fermions on the (001) surface are connected by giant Fermi arcs traversing the entire surface Brillouin zone. These chiral fermions are enforced at the centre or corner of the bulk Brillouin zone by the crystal symmetries, making CoSi a system with only one pair of chiral nodes with large separation in momentum space and extremely long surface Fermi arcs, in sharp contrast to Weyl semimetals, which have multiple pairs of Weyl nodes with small separation. Our results confirm the existence of unconventional chiral fermions and provide a platform for exploring the physical properties associated with chiral fermions. Angle-resolved photoemission spectroscopy measurements in CoSi reveal the presence of unconventional chiral fermions near the Fermi level, with giant surface Fermi arcs and one pair of well separated chiral nodes.
291 citations
TL;DR: In this paper, the authors theoretically study the generic behavior of the penetration depth of the edge states in two-dimensional quantum spin Hall systems and show that the momentum-space width of edge-state dispersion scales with the inverse of penetration depth.
Abstract: We theoretically study the generic behavior of the penetration depth of the edge states in two-dimensional quantum spin Hall systems. We found that the momentum-space width of the edge-state dispersion scales with the inverse of the penetration depth. As an example of well-localized edge states, we take the Bi(111) ultrathin film. Its edge states are found to extend almost over the whole Brillouin zone. Correspondingly, the bismuth (111) 1-bilayer system is proposed to have well-localized edge states in contrast to the HgTe quantum well.
289 citations
TL;DR: In this article, the authors demonstrated the effect of the unique morphology of the resonator reducing the phase mismatch between the optical modes and the hypersound wave, and demonstrated that the resonance of an ultrahigh Q calcium fluoride resonator with 3 µW Brillouin lasing threshold can be observed.
Abstract: Stimulated Brillouin scattering with both pump and Stokes beams in resonance with whispering gallery modes of an ultrahigh Q calcium fluoride resonator is demonstrated for the first time. The resonator is pumped with 1064 nm light and has 3 µW Brillouin lasing threshold. The scattering is observed due to the unique morphology of the resonator reducing the phase mismatch between the optical modes and the hypersound wave.
288 citations
TL;DR: In this paper, the semi-empirical tight binding method is applied to the calculation of the electronic band structures of MoS2, MoSe2, alpha -MoTe2, WS2 and WSe2 in a two dimensional approximation.
Abstract: For pt. II see ibid., vol. 5, 746 (1972). The semiempirical tight binding method is applied to the calculation of the electronic band structures of MoS2, MoSe2, alpha -MoTe2, WS2 and WSe2 in a two dimensional approximation. After a review of the structure and the physical properties of these compounds, the symmetry of the relevant Brillouin zones, including the effects of spin, is discussed. With this material one can fit the calculated band structures of all five compounds to the experimental data. Some of the fine structure of the optical spectra can be interpreted by extending the work into three dimensions. It is also possible to explain some of the properties to which the calculations were not fitted explicitly.
287 citations