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Spin-½
About: Spin-½ is a research topic. Over the lifetime, 40423 publications have been published within this topic receiving 796639 citations.
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TL;DR: In this paper, the authors developed a quantum kinetic theory of current-induced magnetic torques in Rashba-model ferromagnets and derived analytic expressions for relevant limits of a simple model.
Abstract: Motivated by recent experimental studies of thin-film devices containing a single ferromagnetic layer, we develop a quantum kinetic theory of current-induced magnetic torques in Rashba-model ferromagnets. We find that the current-induced spin densities, responsible for the switching behavior, are due most essentially to spin-dependent quasiparticle lifetimes and derive analytic expressions for relevant limits of a simple model. Quantitative model parameter estimates suggest that spin-orbit coupling in the adjacent metal normal magnetic layer must play an essential role in the strength of the switching effect.
156 citations
TL;DR: In this paper, the authors derive and implement symmetry-projected Hartree-Fock-Bogoliubov (HFB) equations and apply them to the molecular electronic structure problem.
Abstract: We derive and implement symmetry-projected Hartree-Fock-Bogoliubov (HFB) equations and apply them to the molecular electronic structure problem. All symmetries (particle number, spin, spatial, and complex conjugation) are deliberately broken and restored in a self-consistent variation-after-projection approach. We show that the resulting method yields a comprehensive black-box treatment of static correlations with effective one-electron (mean-field) computational cost. The ensuing wave function is of multireference character and permeates the entire Hilbert space of the problem. The energy expression is different from regular HFB theory but remains a functional of an independent quasiparticle density matrix. All reduced density matrices are expressible as an integration of transition density matrices over a gauge grid. We present several proof-of-principle examples demonstrating the compelling power of projected quasiparticle theory for quantum chemistry.
156 citations
TL;DR: In this article, the spin magnitude and direction of a black hole resulting from the merger of two black holes with arbitrary masses and spins inspiralling in quasi-circular orbits is predicted.
Abstract: We revisit the problem of predicting the spin magnitude and direction of the black hole resulting from the merger of two black holes with arbitrary masses and spins inspiralling in quasi-circular orbits. We do this by analyzing a catalog of 619 recent numerical-relativity simulations collected from the literature and spanning a large variety of initial conditions. By combining information from the post-Newtonian approximation, the extreme mass-ratio limit and perturbative calculations, we improve our previously proposed phenomenological formulae for the final remnant spin. In contrast with alternative suggestions in the literature, and in analogy with our previous expressions, the new formula is a simple algebraic function of the initial system parameters and is not restricted to binaries with spins aligned/anti-aligned with the orbital angular momentum, but can be employed for fully generic binaries. The accuracy of the new expression is significantly improved, especially for almost extremal progenitor spins and for small mass ratios, yielding a root-mean-square error $\sigma\approx0.002$ for aligned/anti-aligned binaries and $\sigma\approx0.006$ for generic binaries. Our new formula is suitable for cosmological applications and can be employed robustly in the analysis of the gravitational waveforms from advanced interferometric detectors.
156 citations
TL;DR: In this paper, a general Fokker-Planck approach is described to understand and calculate magnetization switching rates and noise in the recently observed phenomenon of spin-torque switching.
Abstract: We describe a general Fokker-Planck approach to understanding and calculating magnetization switching rates and noise in the recently observed phenomenon of spin-torque switching. In this phenomenon, which has possible applications to information storage, a large current passing from a pinned ferromagnetic (FM) layer to a free FM layer switches the free layer. Beginning with Brown [Phys. Rev. 130, 1677 (1963)], switching rates in magnetic systems have been calculated using the Fokker-Planck equation. In the small-oscillation limit, the equations have been solved analytically, giving a first-principles justification for phenomenological effective temperature theories: the spin-torque effect increases the Arrhenius factor $\mathrm{exp}(\ensuremath{-}E∕kT)$ in the switching rate by raising the effective spin temperature $T$. In the present Rapid Communication we generalize the nonlinear Fokker-Planck equation to the case of a Slonczewski spin torque. As an example, we use a linear approximation to calculate telegraph noise rates, leading to good qualitative agreement with recent experiments. However, our nonlinear formulation is also valid for large precessional oscillations. The method also allows the calculation of current-induced magnetic noise in current perpendicular to plane spin valve read heads.
155 citations
TL;DR: It is discovered that both Pd intercalation and substitution induce bulk superconductivity with T(c) up to ~3 K, which competes with DW in a quantum critical pointlike manner.
Abstract: Using transmission electron microscopy, the anomalies in resistivity and magnetic susceptibility at ~262 K in IrTe2 are found to accompany the superlattice peaks with q[over q=(1/5,0,-1/5). The wave vector is consistent with our theoretical calculation for the Fermi surface nesting vector, indicating that the ~262 K transition is of the charge-orbital density wave (DW) type. We also discovered that both Pd intercalation and substitution induce bulk superconductivity with T(c) up to ~3 K, which competes with DW in a quantum critical pointlike manner.
155 citations