TOPICAL REVIEW — Fundamental research under high magnetic fields
The discovery of superconductivity in quasi-one-dimensional Cr-based pnictides A2Cr3As3 (A=alkali metals) has generated considerable research interest, primarily owing to their reduced dimensionality, significant electron correlations, and possible unconventional superconductivity. The upper critical field (Hc2) provides important information on the superconducting pairing. In this paper, we first briefly overview the latest research progress on the Cr-based superconductors. Then, we introduce typical Hc2(T) behaviors of type-Ⅱ superconductors in relation with the pair-breaking mechanisms. After a description of the measurement method for Hc2, we focus on the analysis of Hc2 data, especially for the temperature and angle dependence, in K2Cr3As3 crystals. The result indicates (i) an absence of Pauli-paramagnetic pair breaking for field perpendicular to the Cr3As3 chains, and (ii) a unique threefold modulation for the in-plane Hc2(φ) profile. Finally we conclude with remarks on the possible unconventional superconducting pairing symmetry.
Quantum computation provides a great speedup over its classical counterpart in solving some hard problems. The advantages of quantum computation come from the coherent superposition principle of quantum mechanics. Spin system is one of the most significant candidates to realize quantum computation. In this review, we focus on the recent experimental progress related to quantum coherence and some fundamental concepts such as the uncertainty principle in the spin systems. We shall first briefly introduce the quantum description of qubit, coherence, and decoherence. Based on this picture, preserving quantum coherence and detection of weak magnetic fields are presented. We also discuss the realization of precise quantum coherent control, adiabatic quantum factorization algorithm, and two aspects of uncertainty relations.
Recently, the Dirac and Weyl semimetals have attracted extensive attention in condensed matter physics due to both the fundamental interest and the potential application of a new generation of electronic devices. Here we review the exotic electrical transport phenomena in Dirac and Weyl semimetals. Section 1 is a brief introduction to the topological semimetals (TSMs). In Section 2 and Section 3, the intriguing transport phenomena in Dirac semimetals (DSMs) and Weyl semimetals (WSMs) are reviewed, respectively. The most widely studied Cd3As2 and the TaAs family are selected as representatives to show the typical properties of DSMs and WSMs, respectively. Beyond these systems, the advances in other TSM materials, such as ZrTe5 and the MoTe2 family, are also introduced. In Section 4, we provide perspectives on the study of TSMs especially on the magnetotransport investigations.
We present a review of the principal developments in the evolution and synergism of solute and particle migration in a liquid melt in high-gradient magnetic fields and we also describe their effects on the solidification microstructure of alloys. Diverse areas relevant to various aspects of theory and applications of high-gradient magnetic field-controlled migration of solutes and particles are surveyed. They include introduction, high-gradient magnetic field effects, migration behavior of solute and particles in high-gradient magnetic fields, microstructure evolution induced by high-gradient magnetic fieldcontrolled migrations of solute and particles, and properties of materials modified by high-gradient magnetic field-tailored microstructure. Selected examples of binary and multiphase alloy systems are presented and examined, with the main focus on the correlation between the high-gradient magnetic field-modified migration and the related solidification microstructure evolution. Particular attention is given to the mechanisms responsible for the microstructure evolution induced by highgradient magnetic fields.
High magnetic field is one of the effective tools to control a chemical reaction and materials synthesis. In this review, we summarized the magnetic field effects on chemical reactions, such as reaction pathway, growth behavior of nanomaterials, product phase, and magnetic domain of materials. The surface spins and activity of catalysts under magnetic fields were also discussed.
The characteristics of lattice structures can make crystal possess distinct anisotropic features, such as the varying magnetism in different crystal orientations and different directions. The anisotropic magnetism can also cause the free energy to vary in different orientations of crystal in a magnetic field (magnetic anisotropy energy). Magneto-anisotropy can make the crystal rotate by the magnetic force moment on the crystal with the easy axis towards the direction of the magnetic field, and can also promote the preferential growth along a certain crystal direction at the lowest energy state. By solidification, vapor-deposition, heat treatment, slip casting and electrodeposition under magnetic field, the crystal structure with high grain orientation is obtained in a variety of binary eutectics, peritectic alloys, multicomponent alloys and high temperature superconducting materials. This makes it possible to fabricate texture-functional material by using high magnetic field and magneto-crystalline anisotropy of crystal. The purpose of this article is to review some recent progress of the orientation and alignment in material processing under a high magnetic field.