Zhang Xin-Hui

Evaluation of the Ultrafast Thermal Manipulation of Magnetization Precession in Ferromagnetic Semiconductor (Ga,Mn)As*

We present a quantitative evaluation study of the thermal effect responsible for laser-triggered collective magnetization dynamics in a ferromagnetic (Ga,Mn)As film without applying the external magnetic field by employing the pump-probe magneto-optical spectroscopy. Our observation shows that the effect of ultrafast laser heating on the manipulation of magnetization precession in a (Ga,Mn)As film is not exactly equivalent to that of the ambient temperature increase, and needs to be carefully analyzed by considering the temperature-dependent specific heat of (Ga,Mn)As. The transient modulation of magnetocrystalline anisotropy via ultrafast laser heating at low temperature exhibits a higher sensitivity than that at high temperature. The quantitative analysis of the laser-heating manipulated magnetization precession presented in this work is helpful for evaluating the laser-triggered ultrafast magnetization dynamics in (Ga,Mn)As films.

Topological Structure of Knotted Vortex Lines in Liquid Crystals

In this paper, a novel decomposition expression for the U(1) gauge field in liquid crystals (LCs) is derived. Using this decomposition expression and the -mapping topological current theory, we investigate the topological structure of the vortex lines in LCs in detail. A topological invariant, i.e., the Chern–Simons (CS) action for the knotted vortex lines is presented, and the CS action is shown to be the total sum of all the self-linking and linking numbers of the knot family. Moreover, it is pointed out that the CS action is preserved in the branch processes of the knotted vortex lines.

Knotted Solitons in an Interacting Mixture of a Charged and a Neutral Superfluid for Neutron Stars

By making use of the decomposition of U(1) gauge potential theory and the -mapping method we discuss a mixture of interacting neutral and charged Bose condensates, which is supposed being realized in the interior of neutron stars in the form of a coexistent neutron superfluid and protonic superconductor. We propose that this system possesses vortex lines and two classes of knotted solitons. The topological charge of the vortex lines are characterized by the Hopf indices and the Brower degrees of -mapping, and the knotted solitons are described by nontrivial Hopf invariant and the BF action respectively.

Topological Aspects in an Interacting Mixture of a Charged and a Neutral Superfluid in Neutron Stars

By making use of the decomposition of U(1) gauge potential theory and the o-mapping method we discuss a mixture of interacting neutral and charged Bose condensates, which is supposed to be realized in the interior of neutron stars in the form of a coexistent neutron superfluid and protonic superconductor. We propose that this system possesses vortex line knotted solitons and the topological charges of vortex lines are characterized by the winding numbers of the o-mapping. Furthermore the spatial bifurcation of vortices is also discussed.

Topological structure of Gauss--Bonnet--Chern theorem and p-branes

By making use of the -mapping topological current theory, this paper shows that the Gauss?Bonnet?Chern density (the Euler?Poincar? characteristic ?(M) density) can be expressed in terms of a smooth vector field and take the form of ?(), which means that only the zeros of contribute to ?(M). This is the elementary fact of the Hopf theorem. Furthermore, it presents that a new topological tensor current of -branes can be derived from the Gauss?Bonnet?Chern density. Using this topological current, it obtains the generalized Nambu action for multi -branes.

Self-dual Vortices in Schrödinger–Chern–Simons Model

By making use of the U(1) gauge potential decomposition theory and the -mapping topological current theory, we investigate the Schrodinger–Chern–Simons model in the thin-film superconductor system and obtain an exact Bogomolny self-dual equation with a topological term. It is revealed that there exist self-dual vortices in the system. We study the inner topological structure of the self-dual vortices and show that their topological charges are topologically quantized and labeled by Hopf indices and Brouwer degrees. Furthermore, the vortices are found generating or annihilating at the limit points and encountering, splitting or merging at the bifurcation points of the vector field .

Topological Aspects of Triplet Superconductors

In this paper, using the -mapping theory, it is shown that two kinds of topological defects, i.e., the vortex lines and the monopoles exist in the helical configuration of magnetic field in triplet superconductors. And the inner topological structure of these defects is studied. Because the knot solitons in the triplet superconductors are characterized by the Hopf invariant, we also establish a relationship between the Hopf invariant and the linking number of knots family, and reveal the inner topological structure of the Hopf invariant.

Topological Excitation in Skyrme Theory

Based on the

GaAs/AlGaAs量子井戸における光ゲーティングを介した電子スピン緩和異方性の調整【Powered by NICT】

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Double-color and micro-area reflection type transient spectral measurement system

-mapping topological current theory and the decomposition of gauge potential theory, we investigate knotted vortex lines and monopoles in Skyrme theory and simply discuss the branch processes (splitting, merging and intersection) during the evolution of the monopoles.Based on the -mapping topological current theory and the decomposition of gauge potential theory, we investigate knotted vortex lines and monopoles in Skyrme theory and simply discuss the branch processes (splitting, merging, and intersection) during the evolution of the monopoles.