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Metamagnetic transitions and anomalous magnetoresistance in EuAg4As2 crystals

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Science China(Physics,Mechanics & Astronomy) 2021年第2期64卷 91-97页

作者： QinQing Zhu Liang Li ZhiHua Yang ZheFeng Lou JianHua Du JinHu Yang Bin Chen hangdong wang MingHu Fang Hangzhou Key Laboratory of Quantum Matter Department of PhysicsHangzhou Normal UniversityHangzhou311121China Department of Physics Zhejiang UniversityHangzhou310027China Department of Physics China Jiliang UniversityHangzhou310018China Collaborative Innovation Center of Advanced Microstructures Nanjing UniversityNanjing210093China

In this work,we systematically studied the magnetic and transport properties of EuAg4As2 single *** was found that the two antiferromagnetic transitions(TN1=10 K and TN2=15 K)were driven to lower temperatures by an applied magnetic *** TN1,two successive metamagnetic transitions were observed when a magnetic field was applied in the ab plane(H//abplane).For both H//ab and H//c,EuAg4As2 showed a positive,unexpectedly large magnetoresistance(up to 202%)in lower magnetic fields below TN1,and a large negative magnetoresistance(up to-78%)at high fields/intermediate temperatures,thus presenting potential applications in magnetic ***,the magnetic phase diagrams of EuAg4As2 were constructed for both H//ab and H//c using the resistivity and magnetisation data.

关键词： anomalous magnetoresistance metamagnetic transition magnetic phase diagram

Bulk superconductivity in the Dirac semimetal TlSb

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Science China(Physics,Mechanics & Astronomy) 2021年第4期64卷 96-103页

作者： YuXing Zhou Bin Li ZheFeng Lou HuanCheng Chen Qin Chen BinJie Xu ChunXiang Wu JianHua Du JinHu Yang hangdong wang MingHu Fang Department of Physics Zhejiang UniversityHangzhou 310027China New Energy Technology Engineering Laboratory of Jiangsu Province School of ScienceNanjing University of Posts and TelecommunicationsNanjing 210023China Department of Applied Physics China Jiliang UniversityHangzhou 310018China Department of Physics Hangzhou Normal UniversityHangzhou 310036China Collaborative Innovation Center of Advanced Microstructures Nanjing UniversityNanjing 210093China

A feasible strategy for realizing the Majorana fermions is searching for a simple compound with both bulk superconductivity and Dirac surface *** this paper,we perform calculations of electronic band structure,the Fermi surface,and the surface states,and measure the resistivity,magnetization,and specific heat of a TlSb compound with a CsCl-type *** band structure calculations show that TlSb is a Dirac semimetal when spin-orbit coupling is *** is first determined to be a type-Ⅱsuperconductor with T_(c)=4.38 K,Hc1(0)=148 Oe,H_(c2)(0)=1.12 T,andκ_(GL)=*** also confirm that TlSb is a moderately coupled s-wave *** we cannot determine the band near the Fermi level EF that is responsible for superconductivity,its coexistence with topological surface states implies that the TlSb compound may be a simple material platform to realize the fault-tolerant quantum computations.

关键词： s-wave superconductor Dirac semimetal topological superconductor

Effect of annealing on superconductivity in Fe_(1+y)(Te_(1-x)S_x) system

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Science China(Physics,Mechanics & Astronomy) 2010年第7期53卷 1216-1220页

作者： DONG ChiHeng wang hangdong YANG JinHu QIAN Bin CHEN Jian LI ZuJuan YUAN HuiQiu FANG MingHu Department of Physics Zhejiang UniversityHangzhou 310027China Department of Physics Changshu Institute of TechnologyChangshu 215500China

We have synthesized polycrystalline samples of Fe1.11(Te1-xSx) and single crystals of Fe1+y(Te0.88S0.12),and characterized their *** results show that the solid solution of S in the Fe1.11Te tetragonal lattice is limited,~10%.We observed superconductivity at ~8 K in both polycrystalline samples and single *** measurements reveal that the volume fraction is small for this superconducting phase in both polycrystalline samples as-synthesized and single crystals *** is found that annealing in air enhances the superconducting fraction;the maximum fraction is almost 100% in the single crystals annealed in air at 300°*** discuss the effect of annealing on superconductivity and transport properties at the normal state in the Fe1+y(Te1-xSx) system in terms of decrease of the excess Fe.

关键词： Fe-Based superconductors Fe1+y(Te1-xSx)single crystal annealing effect

Large unsaturated positive and negative magnetoresistance in Weyl semimetal TaP

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Science China(Physics,Mechanics & Astronomy) 2016年第5期59卷 21-26页

作者： JianHua Du hangdong wang Qin Chen OianHui Mao Rajwali Khan BinJie XU YuXing Zhou YanNan Zhang JinHu Yang Bin Chen ChunMu Feng MingHu Fang Department of Physics Zhejiang University Hangzhou 310027 China Department of Physics Hangzhou Normal University Hangzhou 310036 China Collaborative Innovation Center of Advanced Microstructures Nanjing 210093 China

After successfully growing single-crystal TaP, we measured its longitudinal resistivity （Pxx） and Hall resistivity （Pyx） at magnetic fields up to 9 T in the temperature range of 2-300 K. At 8 T, the magnetoresistance （MR） reached 3.28 ×10^5% at 2 K, 176% at 300 K. Neither value appeared saturated. We confirmed that TaP is a hole-electron compensated semimetal with a low carrier concentration and high hole mobility ofμh=3.71 × 105 cm2/V s, and found that a magnetic-field-induced metal-insulator transition occurs at room temperature. Remarkably, because a magnetic field （H） was applied in parallel to the electric field （E）, a negative MR due to a chiral anomaly was observed and reached -3000% at 9 T without any sign of saturation, either, which is in contrast to other Weyl semimetals （WSMs）. The analysis of the Shubnikov-de Haas （SdH） oscillations superimposed on the MR revealed that a nontrivial Berry＇s phase with a strong offset of 0.3958, which is the characteristic feature of charge carriers enclosing a Weyl node. These results indicate that TaP is a promising candidate not only for revealing fundamental physics of the WSM state but also for some novel applications.

关键词： Weyl semimetal positive and negative magnetoresistance Weyl fermions

Quantum critical behavior in an antiferromagnetic heavy-fermion Kondo lattice system(Ce(1-x)Lax)2Ir3Ge5

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Chinese Physics B 2017年第1期26卷 438-443页

作者： Rajwali Khan Qianhui Mao hangdong wang Jinhu Yang Jianhua Du Binjie Xu Yuxing Zhou Yannan Zhang Bing Chen Minghu Fang Department of Physics Zhejiang University Hangzhou 310027 China Department of Physics Hangzhou Normal University Hangzhou 310036 China Collaborative Innovation Center of Advanced Microstructures Nanfing 210093 China

The measurements on temperature dependences of magnetic susceptibility χ（T）, specific heat C（T）, and electrical resistivity ρ（T） were carried out for the antiferromagnetic（AFM）（Ce（1-x）Lax）2Ir3Ge5（0 ≤ x ≤ 0.66） system. It was found that the Neel temperature TNdecreases with increasing La content x, and reaches 0 K near a critical content xcr =0.6. A new phase diagram was constructed based on these measurements. A non-Fermi liquid behavior in ρ（T） and a log T relationship in C（T） were found in the samples near xcr, indicating them to be near an AFM quantum critical point（QCP） with strong spin fluctuation. Our finding indicates that（Ce（1-x）Lax）2Ir3Ge5 may be a new platform to search for unconventional superconductivity.

关键词： quantum critical point antiferromagnetic Kondo lattice system (Ce1-xLax)2Ir3Ge5

Large Magnetoresistance and Nontrivial Berry Phase in Nb_(3)Sb Crystals with A15 Structure

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Chinese Physics Letters 2021年第8期38卷 110-114页

作者： Qin Chen Yuxing Zhou Binjie Xu Zhefeng Lou Huancheng Chen Shuijin Chen Chunxiang Wu Jianhua Du hangdong wang Jinhu Yang Minghu Fang Department of Physics Zhejiang UniversityHangzhou 310027China Department of Applied Physics China Jiliang UniversityHangzhou 310018China Department of Physics Hangzhou Normal UniversityHangzhou 310036China Collaborative Innovation Center of Advanced Microstructure Nanjing UniversityNanjing 210093China

Compounds with the A15 structure have attracted extensive attention due to their superconductivity and nontrivial topological band *** have successfully grown Nb_(3)Sb single crystals with the A15 structure and systematically measured the longitudinal resistivity,Hall resistivity and quantum oscillations in *** to other topological trivial/nontrivial semimetals,Nb_(3)Sb exhibits large magnetoresistance(MR)at low temperatures(717%,2 K and 9 T),unsaturating quadratic field dependence of MR and up-turn behavior in ρ_(xx)(T)curves under magnetic field,which is considered to result from a perfect hole-electron compensation,as evidenced by the Hall resistivity *** nonzero Berry phase obtained from the de-Hass van Alphen(dHvA)oscillations demonstrates that Nb_(3)Sb is topologically *** results indicate that Nb_(3)Sb superconductor is also a semimetal with large MR and nontrivial Berry *** indicates that Nb_(3)Sb may be another platform to search for the Majorana zero-energy mode.

关键词： nontrivial Berry topological

Polymorphism and superconductivity in the V-Nb-Mo-Al-Ga high-entropy alloys

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Science China Materials 2020年第5期63卷 823-831页

作者： Jifeng Wu Bin Liu Yanwei Cui Qinqing Zhu Guorui Xiao hangdong wang Siqi Wu Guanghan Cao Zhi Ren Department of Physics Fudan UniversityShanghai 200433China School of Science Westlake UniversityHangzhou 310024China Institute of Natural Sciences Westlake Institute for Advanced StudyHangzhou 310024China Department of Physics Zhejiang UniversityHangzhou 310027China Department of Physics Hangzhou Normal UniversityHangzhou 310036China

High-entropy alloys(HEAs)are the focus of current research for their diverse properties,including superconductivity and structural ***,the polymorphic transition has been observed only in nonsuperconducting HEAs mostly under high *** we report the discovery of the superconductivity and temperature-driven polymorphism in(V0.5Nb0.5)3-xMoxAl0.5Ga0.5(0.2≤x≤1.4)HEAs,which are of a single body-centered cubic(bcc)structure for x=0.2 and a mixture of the bcc and A15 structures for higher x *** annealing,the bcc structure undergoes a polymorphic transformation to the A15 one and all HEAs exhibit bulk *** the sample with x=0.2,the bcc polymorph is not superconducting down to1.8 K,whereas the A15 polymorph has a superconducting transition temperature Tc of 10.2 K and estimated zero-temperature upper critical field Bc2(0)of 20.1 T,both of which are the highest among HEA *** increasing Mo content x,both Tc and Bc2(0)of the A15-type HEAs decrease,yet the large ratio of Bc2(0)/Tc signifies a disorder-induced enhancement of the upper critical field over a wide x *** decrease in Tc is attributed to the decrease in both the electronic specific-heat coefficient and electron-phonon coupling ***,the valence electron count dependence of Tc,which is different from both the binary A15 and other structurally different HEA superconductors,suggests that Tc may be increased further by reducing the number of valence *** results not only uncover HEA superconductors of a new structural type,but also provide the first example of polymorphism-dependent superconductivity in HEAs.

关键词： polymorphsim superconductivity V-Nb-Mo-Al-Ga high-entropy alloys

Magnetoresistance and Kondo Effect in Nodal-Line Semimetal VAs_(2)

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Chinese Physics Letters 2021年第1期38卷 92-98页

作者： Shuijin Chen Zhefeng Lou Yuxing Zhou Qin Chen Binjie Xu Chunxiang Wu Jianhua Du Jinhu Yang hangdong wang Minghu Fang Department of Physics Zhejiang UniversityHangzhou 310027China Department of Applied Physics China Jiliang UniversityHangzhou 310018China Department of Physics Hangzhou Normal UniversityHangzhou 310036China Collaborative Innovation Center of Advanced Microstructures Nanjing UniversityNanjing 210093China

We performed calculations of the electronic band structure and the Fermi surface,measured the longitudinal resistivity ρxx(T,H),Hall resistivity ρxy(T,H),and magnetic susceptibility as a function of temperature at various magnetic fields for VAs_(2) with a monoclinic crystal *** band structure calculations show that VAs_(2) is a nodal-line semimetal when spin-orbit coupling is *** emergence of a minimum at around11 K in ρxx(T) measured at H=0 demonstrates that some additional magnetic impurities(V^(4+),S=1/2)exist in VAs_(2) single crystals,inducing Kondo scattering,evidenced by both the fitting of ρxx(T) data and the susceptibility *** is found that a large positive magnetoresistance(MR) reaching 649% at 10 K and 9 T,its nearly quadratic field dependence,and a field-induced up-turn behavior of ρxx(T) also emerge in VAs_(2),although MR is not so large due to the existence of additional scattering compared with other topological nontrivial/trivial *** observed properties are attributed to a perfect charge-carrier compensation,which is evidenced by both the calculations relying on the Fermi surface and the Hall resistivity *** results indicate that the compounds containing V(3d^(3)4s^(2)) element can be as a platform for studying the influence of magnetic impurities to the topological properties.

关键词： resistance Kondo resistivity

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直线加速度所致的猫弥漫性轴突损伤

中华神经外科杂志 1997年第1期13卷 31-33页

作者：王汉东段国升张纪周定标罗毅南京军区南京总医院神经外科解放军总医院神经外科

目的：为了解直线加速度在颅脑损伤特别是在弥漫性轴突损伤（ＤＡＩ）中的作用。方法：用一套撞击装置对２６只猫进行实验。结果：直线加速度可以导致几乎所有类型的颅脑损伤，包括颅骨骨折、蛛网膜下腔出血、硬膜下血肿、硬膜外血肿、... 详细信息

目的：为了解直线加速度在颅脑损伤特别是在弥漫性轴突损伤（ＤＡＩ）中的作用。方法：用一套撞击装置对２６只猫进行实验。结果：直线加速度可以导致几乎所有类型的颅脑损伤，包括颅骨骨折、蛛网膜下腔出血、硬膜下血肿、硬膜外血肿、脑挫伤、脑干损伤，特别是ＤＡＩ。ＤＡＩ的特征性改变－轴突回缩球在２４小时内死亡的动物脑标本中看不到，２４小时后可见到，７２小时则多而典型，７天时仍然存在。结论：凡能使脑的神经纤维受到广泛剪力和（或）张力的任何形式的外部作用均可产生ＤＡＩ。

关键词：颅脑损伤弥漫性轴突损伤直线加速度