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    Recent progress on magnetic-field studies on quantum-spin-liquid candidates
    Zhen Ma(马祯), Kejing Ran(冉柯静), Jinghui Wang(王靖珲), Song Bao(鲍嵩), Zhengwei Cai(蔡正蔚), Shichao Li(李世超), Jinsheng Wen(温锦生)
    Chin. Phys. B, 2018, 27 (10): 106101.   DOI: 10.1088/1674-1056/27/10/106101
    Abstract414)   HTML    PDF (3850KB)(349)      
    Quantum spin liquids (QSLs) represent a novel state of matter in which quantum fluctuations prevent the conventional magnetic order from being established, and the spins remain disordered even at zero temperature. There have been many theoretical developments proposing various QSL states. On the other hand, experimental movement was relatively slow largely due to limitations on the candidate materials and difficulties in the measurements. In recent years, the experimental progress has been accelerated. In this topical review, we give a brief summary of experiments on the QSL candidates under magnetic fields. We arrange our discussions by two categories:i) Geometrically-frustrated systems, including triangular-lattice compounds YbMgGaO4 and YbZnGaO4, κ-(BEDT-TTF)2Cu2(CN)3, and EtMe3Sb[Pd(dmit)2]2, and the kagomé system ZnCu3(OH)6Cl2; ii) the Kitaev material α-RuCl3. Among these, we will pay special attention to α-RuCl3, which has been intensively studied by ours and other groups recently. We will present evidence that both supports and rejects the QSL ground state for these materials, based on which we give several perspectives to stimulate further research activities.
    Superconductivity with peculiar upper critical fields in quasi-one-dimensional Cr-based pnictides
    Guang-Han Cao(曹光旱), Zeng-Wei Zhu(朱增伟)
    Chin. Phys. B, 2018, 27 (10): 107401.   DOI: 10.1088/1674-1056/27/10/107401
    Abstract316)   HTML    PDF (5950KB)(370)      

    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.

    Heavy fermions in high magnetic fields
    M Smidman, B Shen(沈斌), C Y Guo(郭春煜), L Jiao(焦琳), X Lu(路欣), H Q Yuan(袁辉球)
    Chin. Phys. B, 2019, 28 (1): 017106.   DOI: 10.1088/1674-1056/28/1/017106
    Abstract311)   HTML    PDF (7769KB)(299)      
    Heavy fermion materials are prototypical strongly correlated electron systems, where the strong electron–electron interactions lead to a wide range of novel phenomena and emergent phases of matter. Due to the low energy scales, the relative strengths of the Ruderman–Kittel–Kasuya–Yosida (RKKY) and Kondo interactions can often be readily tuned by non-thermal control parameters such as pressure, doping, or applied magnetic fields, which can give rise to quantum criticality and unconventional superconductivity. Here we provide a brief overview of research into heavy fermion materials in high magnetic fields, focussing on three main areas. Firstly we review the use of magnetic fields as a tuning parameter, and in particular the ability to realize different varieties of quantum critical behaviors. We then discuss the properties of heavy fermion superconductors in magnetic fields, where experiments in applied fields can reveal the nature of the order parameter, and induce new novel phenomena. Finally we report recent studies of topological Kondo systems, including topological Kondo insulators and Kondo–Weyl semimetals. Here experiments in magnetic fields can be used to probe the topologically non-trivial Fermi surface, as well as related field-induced phenomena such as the chiral anomaly and topological Hall effect.
    Physics of quantum coherence in spin systems
    Maimaitiyiming Tusun(麦麦提依明·吐孙), Xing Rong(荣星), Jiangfeng Du(杜江峰)
    Chin. Phys. B, 2019, 28 (2): 024204.   DOI: 10.1088/1674-1056/28/2/024204
    Abstract574)   HTML    PDF (9653KB)(490)      

    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.

    Electron transport in Dirac and Weyl semimetals
    Huichao Wang(王慧超), Jian Wang(王健)
    Chin. Phys. B, 2018, 27 (10): 107402.   DOI: 10.1088/1674-1056/27/10/107402
    Abstract409)   HTML    PDF (6382KB)(387)      

    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.

    High-gradient magnetic field-controlled migration of solutes and particles and their effects on solidification microstructure: A review
    Tie Liu(刘铁), Qiang Wang(王强), Yi Yuan(苑轶), Kai Wang(王凯), Guojian Li(李国建)
    Chin. Phys. B, 2018, 27 (11): 118103.   DOI: 10.1088/1674-1056/27/11/118103
    Abstract438)   HTML    PDF (9066KB)(267)      

    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.

    Magnetochemistry and chemical synthesis
    Lin Hu(胡林), Guoliang Xia(夏国良), Qianwang Chen(陈乾旺)
    Chin. Phys. B, 2019, 28 (3): 037102.   DOI: 10.1088/1674-1056/28/3/037102
    Abstract504)   HTML    PDF (5616KB)(337)      

    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.

    Orientation and alignment during materials processing under high magnetic fields
    Zhong-Ming Ren(任忠鸣), Jiang Wang(王江), Rui-Xin Zhao(赵睿鑫)
    Chin. Phys. B, 2019, 28 (4): 048301.   DOI: 10.1088/1674-1056/28/4/048301
    Abstract511)   HTML    PDF (2433KB)(319)      

    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.

    High-magnetic-field induced charge order in high-Tc cuprate superconductors
    L X Zheng(郑立玄), J Li(李建), T Wu(吴涛)
    Chin. Phys. B, 2019, 28 (11): 117402.   DOI: 10.1088/1674-1056/ab4575
    Abstract256)   HTML    PDF (15444KB)(208)      
    In the last few years, charge order and its entanglement with superconductivity are under hot debate in high-Tc community due to the new progress on charge order in high-Tc cuprate superconductors YBa2Cu3O6+x. Here, we will briefly introduce the experimental status of this field and mainly focus on the experimental progress of high-field nuclear magnetic resonance (NMR) study on charge order in YBa2Cu3O6+x. The pioneering high-field NMR work in YBa2Cu3O6+x sets a new stage for studying charge order which has become a ubiquitous phenomenon in high-Tc cuprate superconductors.
    Specific heat in superconductors
    Hai-Hu Wen(闻海虎)
    Chin. Phys. B, 2020, 29 (1): 017401.   DOI: 10.1088/1674-1056/ab5a3d
    Abstract396)   HTML    PDF (6693KB)(416)      
    Specific heat is a powerful tool to investigate the physical properties of condensed materials. Superconducting state is achieved through the condensation of paired electrons, namely, the Cooper pairs. The condensed Cooper pairs have lower entropy compared with that of electrons in normal metal, thus specific heat is very useful in detecting the low lying quasiparticle excitations of the superconducting condensate and the pairing symmetry of the superconducting gap. In this brief overview, we will give an introduction to the specific heat investigation of the physical properties of superconductors. We show the data obtained in cuprate and iron based superconductors to reveal the pairing symmetry of the order parameter.
    Lorentz transmission electron microscopy for magnetic skyrmions imaging
    Jin Tang(汤进), Lingyao Kong(孔令尧), Weiwei Wang(王伟伟), Haifeng Du(杜海峰), Mingliang Tian(田明亮)
    Chin. Phys. B, 2019, 28 (8): 087503.   DOI: 10.1088/1674-1056/28/8/087503
    Abstract462)   HTML    PDF (3708KB)(398)      
    Magnetic skyrmions have interesting properties, including their small size, topological stability, and extremely low threshold current for current-driven motion. Therefore, they are regarded as promising candidates for next-generation magnetic memory devices. Lorentz transmission electron microscopy (TEM) has an ultrahigh magnetic domain resolution (~2 nm), it is thus an ideal method for direct real-space imaging of fine magnetic configurations of ultra-small skyrmions. In this paper, we describe the basic principles of Lorentz-TEM and off-axis electron holography and review recent experimental developments in magnetic skyrmion imaging using these two methods.