Asymmetric spin-wave dispersion due to Dzyaloshinskii-Moriya interaction in an ultrathin Pt/CoFeB film

Employing Brillouin spectroscopy, strong interfacial Dzyaloshinskii-Moriya interactions have been observed in an ultrathin Pt/CoFeB film. Our micromagnetic simulations show that spin-wave nonreciprocity due to asymmetric surface pinning is insignificant for the 0.8nmthick CoFeB film studied. The observed high asymmetry of the monotonic spin wave dispersion relation is thus ascribed to strong Dzyaloshinskii-Moriya interactions present at the Pt/CoFeB interface. Our findings should further enhance the significance of CoFeB as an important material for magnonic, spintronic and skyrmionic applications.Comment: 12 pages, 4 figure

Time evolution of coupled-bunch modes from beta function variation in storage rings

We present an analytical and numerical study of the equations of motion for bunches coupled by transverse wakefields. We base our study on a recent lattice design for the damping rings in the baseline configuration of the International Linear Collider. Using the macroparticle model, and assuming resistive wall wakefield coupling, we present numerical results on the time evolution of the multibunch modes. Decay modes display growth after initial decay, and mode amplitudes exhibit high-frequency oscillations. These phenomena are not expected if the beta function is assumed to have a constant, averaged value. We show analytically that they can come from coupling between modes caused by variation of the beta function in a real lattice. The effect is shown to be comparable to the effect of a nonuniform fill pattern and significantly larger than that of the higher-order mode wakefield localized in the rf cavities. Turning to the case of constant beta function, we develop a more complete treatment of the equations of motion. We derive general formulas for the bunch trajectories, and show that such formulas can only be valid in the limit of small wakefield coupling

Reproduction of spin-orbit splitting with the inclusion of nuclear tensor using seniority force

Prior to embarking on investigations with nuclear tensor, we performed a benchmark study to check the validity of our Skyrme-Hartree-Fock-BCS code. We repeat the fit of SLy5+tensor parametrization but using the seniority force. Our code reproduced the trend obtained in previous study for both SLy5 and SLy5+tensor

Preliminary study of ground state properties of odd-mass nuclei using the SLy5* within the Skyrme mean-field approach

International audienceThe single-particle states are degenerate in the ground-state of an even-even nucleus since there are at least two states (corresponding to spin up and spin down) with the same energy. However, this is not the case for odd-mass nucleus due to the existence of the unpaired nucleon which breaks the time reversal symmetry. The impact of the time-reversal symmetry breaking on a wide range of rare earth nuclei has been investigated recently within the Skyrme mean-field approach using the Skyrme SIII parametrization [1]. In order to have a more complete assessment on the impact of time-reversal symmetry breaking on nuclear properties, we performed calculations using the SLy5* parametrization with BCS pairing. The seniority force is used to approximate the residual pairing interaction. In this work, some nuclear properties of odd-mass rare earth nuclei namely binding energy, nuclear charge radii, spectroscopic charge quadrupole moment and band-head energy spectra are compared to previous SIII calculations and experimental data

Consistency of two different approaches to determine the strength of a pairing residual interaction in the rare-earth region

Two fits of the pairing residual interaction in the rare-earth region are independently performed. One is made on the odd-even staggering of masses by comparing measured and explicitly calculated three-point binding-energy differences centered on odd-even nuclei. Another deals with the moments of inertia of the first 2+ states of well-deformed even-even nuclei upon comparing experimental data with the results of Inglis-Belyaev moments (supplemented by a crude estimate of the so-called Thouless-Valatin corrections). The sample includes 24 even-even and 31 odd-mass nuclei selected according to two criteria: They should have good rotor properties and should not correspond to low pairing-correlation regimes in their ground states. Calculations are performed in the self-consistent Hartree-Fock plus BCS framework (implementing a self-consistent blocking in the case of odd-mass nuclei). The Skyrme SIII parametrization is used in the particle-hole channel and the fitted quantities are the strengths of |Tz|=1 proton and neutron seniority residual interactions. As a result, the two fits yield sets of strengths in excellent agreement: about 0.1% for the neutron parameters and 0.2% for protons. In contrast, when one performs such a fit on odd-even staggering from quantities deduced from BCS gaps or minimal quasiparticle energies in even-even nuclei, as is traditional, one obtains results significantly different from those obtained in the same nuclei by a fit of moments of inertia. As a conclusion, beyond providing a phenomenological tool for microscopic calculations in this region, we have illustrated the proposition performed in the seminal paper of Bohr et al. [Phys. Rev. 110, 936 (1958)PHRVAO0031-899X10.1103/PhysRev.110.936] that moments of inertia and odd-even staggering in selected nuclei were excellent measuring sticks of nuclear pairing correlations. Furthermore, we have assessed the validity of our theoretical approach which includes simple yet apparently reasonable assumptions (seniority residual interaction, parametrization of its matrix elements as functions of the nucleon numbers, and global Thouless-Valatin renormalization of Inglis-Belyaev moments of inertia)

Enhancement of spin-wave nonreciprocity in magnonic crystals via synthetic antiferromagnetic coupling

10.1038/srep10153Scientific Reports

Collective Coupling between Intrinsic Vortical and Global Rotation Modes Revisited

The reduction of the moments of inertia (MoI) in well deformed nuclei from their rigid body values has been one of the reasons leading Bohr, Mottelson and Pines to propose the description of low-energy nuclear states by BCS-type wavefunctions. This quenching has latter been understood by Mottelson and Valatin in terms of a collective coupling of intrinsic and global rotation modes. In this paper, we review a quantitatively very satisfactory account of this coupling in the framework of so-called Chandrasekhar's S-ellipsoid velocity fields. Another experimental fact at the origin of the BCS wavefunction proposal is the systematic odd-even staggering (OES) of masses observed between odd-A and even-even nuclei. Through a simple self-consistent description of these masses we have shown that with the same parametrization of the residual interaction V_res one is able to reproduce very well both the MoI and OES effects