All-optical spin switching is a potential trailblazer for information storage and communication at an unprecedented fast rate and free of magnetic fields. However, the current wisdom is largely based on semiempirical models of effective magnetic fields and heat pulses, so it is difficult to provide high-speed design protocols for actual devices. Here, we carry out a massively parallel first-principles and model calculation for thirteen spin systems and magnetic layers, free of any effective field, to establish a simpler and alternative paradigm of laser-induced ultrafast spin reversal and to point out a path to a full-integrated photospintronic device. It is the interplay of the optical selection rule and sublattice spin orderings that underlines seemingly irreconcilable helicity-dependent/independent switchings. Using realistic experimental parameters, we predict that strong ferrimagnets, in particular, Laves phase C15 rare-earth alloys, meet the telecommunication energy requirement of 10 fJ, thus allowing a cost-effective subpicosecond laser to switch spin in the GHz region.Comment: 23 pages, 6 figures and one tabl

Nanostructured transition metal sulfides are promising anode materials for lithium-ion batteries. Nevertheless, it is still a great challenge to prepare capacity-improved electrodes without reducing their rate capability and cycle stability. In this paper, we present a C/Co9S8@SnS2 composite material by loading SnS2 nanocrystals onto MOF-derived C/Co9S8 nanostructures. The C/Co9S8@SnS2 composite has multiple active sites to store lithium ions. The specific capacity reaches 3.1 mAh cm−2 when the current density is 0.224 mA cm−2. The asynchronous electrochemical reaction between Co9S8 and SnS2 offsets the volume expansion of the anode material. Meanwhile, the compact adhesion of carbon layers on the interfaces suppresses the destruction of the anode during the charging–discharging processes. Consequently, the synthesized electrode presents favorable capacity with high current density or under long-term cycling conditions. The prepared battery has a reversible specific capacity of 0.452 mAh cm−2 and a coulomb efficiency of 99.7% after 500 cycles with a high current density of 2.24 mA cm−2. The research results obtained in this work provides a feasible strategy to improve the performance of electrodes systematically.

Light fields with structured polarization distribution interacting with structured media will result in many novel optical effects in both the linear and nonlinear regimes. In this work, we report a theoretical investigation of both vectorial self-diffraction behaviors and polarization evolution characteristics of a radially polarized beam induced by anisotropic Kerr nonlinearity. By taking the polarization-orientation dependence of the third-order refractive nonlinearity, we study the far-field vectorial self-diffraction patterns of the radially polarized beam using the vectorial Rayleigh-Sommerfeld formulas. Numerical results reveal that the self-diffraction patterns with a four-fold rotational symmetry exhibit hybrid states of polarization. Moreover, the interaction of radially polarized beams with the anisotropic nonlinear Kerr media leads to the redistribution of the spin angular momentum (SAM) flux in the far-field plane. The presented work opens up new avenues for varying polarization and SAM through anisotropic optical nonlinearity.

No abstract

No abstract