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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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TL;DR: The k-space spectral evolution directly demonstrates, for the first time, that the CDW order parameter microscopically competes with superconductivity in the same band.
Abstract: A superconducting state (T(c) approximately 4.2 K) has very recently been observed upon successful doping of the charge-density-wave (CDW) ordered triangular lattice TiSe(2), with copper. Using state-of-the-art photoemission spectroscopy we identify, for the first time, momentum-space locations of doped electrons that form the Fermi sea of the superconductor. With doping, we find that kinematic nesting volume increases, whereas coherence of the CDW collective order sharply drops. In superconducting doping, as chemical potential rises, we observe the emergence of a large density of states in the form of a narrow electron pocket near the L point of the Brillouin zone with d-like character. The k-space spectral evolution directly demonstrates, for the first time, that the CDW order parameter microscopically competes with superconductivity in the same band.
72 citations
TL;DR: The results show a silicene-derived band with a clear gap and linear energy-momentum dispersion near the Fermi level at the Γ symmetry point of the (3 × 3) phase at several distinctive Brillouin zones, suggesting a limited silicenes-silver hybridization in disagreement with recent density-functional theory (DFT) predictions.
Abstract: By mapping the low-energy electronic dynamics using angle resolved photoemission spectroscopy (ARPES), we have shed light on essential electronic characteristics of the (3 × 3) silicene phase on Ag(111) surfaces. In particular, our results show a silicene-derived band with a clear gap and linear energy-momentum dispersion near the Fermi level at the Γ symmetry point of the (3 × 3) phase at several distinctive Brillouin zones. Moreover, we have confirmed that the large buckling of ~0.7 A of this silicene structure induces the opening of a gap close to the Fermi level higher than at least 0.3 eV, in agreement with recent reported photoemission results. The two-dimensional character of the charge carriers has also been revealed by the photon energy invariance of the gapped silicene band, suggesting a limited silicene-silver hybridization, in disagreement with recent density-functional theory (DFT) predictions.
72 citations
TL;DR: In this article, it was shown that in a wide range of experimentally accessible regimes where the in-plane magnetic field is higher than the Pauli limit field but lower than $H 2 c 2, a 2H-structure monolayer NbSe$_2$ or simiarly TaS$_ 2$ becomes a nodal topological superconductor.
Abstract: Recently, Ising superconductors which possess in-plane upper critical fields much larger than the Pauli limit field are under intense experimental study. Many monolayer or few layer transition metal dichalcogenides are shown to be Ising superconductors. In this work, we show that in a wide range of experimentally accessible regimes where the in-plane magnetic field is higher than the Pauli limit field but lower than $H_{c2}$, a 2H-structure monolayer NbSe$_2$ or simiarly TaS$_2$ becomes a nodal topological superconductor. The bulk nodal points appear on the $\Gamma- M$ lines of the Brillouin zone where the Ising SOC vanishes. The nodal points are connected by Majorana flat bands, similar to the Weyl points being connected by surface Fermi arcs in Weyl semimetals. The Majorana flat bands are associated with a large number of zero energy Majorana fermion edge modes which induce spin-triplet Cooper pairs. This work demonstrates an experimentally feasible way to realise Majorana fermions in nodal topological superconductor, without any fining tuning of experimental parameters.
72 citations
TL;DR: In this paper, the authors used neutron scattering to show that the phase transition in the 2D honeycomb lattice is a weakly first order transition and controlled by spin-orbit coupling (SOC) induced magnetic anisotropy.
Abstract: We use neutron scattering to show that ferromagnetic (FM) phase transition in the two-dimensional (2D) honeycomb lattice ${\mathrm{CrI}}_{3}$ is a weakly first order transition and controlled by spin-orbit coupling (SOC) induced magnetic anisotropy, instead of magnetic exchange coupling as in a conventional ferromagnet. With increasing temperature, the magnitude of magnetic anisotropy, seen as a spin gap at the Brillouin zone center, decreases in a power law fashion and vanishes at ${T}_{C}$, while the in-plane and $c$-axis spin-wave stiffnesses associated with magnetic exchange couplings remain robust at ${T}_{C}$. We also compare parameter regimes where spin waves in ${\mathrm{CrI}}_{3}$ can be described by a Heisenberg Hamiltonian with Dzyaloshinskii-Moriya interaction or a Heisenberg-Kitaev Hamiltonian. These results suggest that the SOC induced magnetic anisotropy plays a dominant role in stabilizing the FM order in single layer 2D van der Waals ferromagnets.
72 citations
Journal Article•
TL;DR: In this article, the electron-doped superconductor Nd 2 - x Ce x CuO 4 (x = 0.15, T c = 22 K) has revealed a nonmonotonic d x 2 - y 2 superconducting order parameter.
Abstract: Low energy polarized electronic Raman scattering of the electron-doped superconductor Nd 2 - x Ce x CuO 4 (x = 0.15, T c = 22 K) has revealed a nonmonotonic d x 2 - y 2 superconducting order parameter. It has a maximum gap of 4.4k B T c at Fermi surface intersections with an antiferromagnetic Brillouin zone (the "hot spots") and a smaller gap of 3.3k B T c at fermionic Brillouin zone boundaries. The gap enhancement in the vicinity of the hot spots emphasizes the role of antiferromagnetic fluctuations and the similarity in the origin of superconductivity for electron- and hole-doped cuprates.
72 citations