The magnetic phase diagram of rare-earth perovskite compound,GdScO3,has been investigated by magnetization and heat capacity.The system undergoes an antiferromagnetic phase transition at TN=2.6 K,with an easy axis of ...The magnetic phase diagram of rare-earth perovskite compound,GdScO3,has been investigated by magnetization and heat capacity.The system undergoes an antiferromagnetic phase transition at TN=2.6 K,with an easy axis of magnetization along the a axis.The magnetization measurements show that it exists a spin-flop transition around 0.3 T for the applied field along the a axis.The critical magnetic field for the antiferromagnetic-to-paramagnetic transition is near 3.2 T when temperature approaches zero.By scaling susceptibilities,we presume this point(B=3.2 T,T=0 K)might be a fieldinduced quantum critical point and the magnetic critical fluctuations can even be felt above TN.展开更多
The recently discovered metal-intercalated iron selenide superconductors A2Fe4Se5 （A=K, Cs, T1- K, Rb, T1-Rb） （245） compounds, with Tc ～30K, have attracted much interest A high transition- temperature （TN ≈ 470...The recently discovered metal-intercalated iron selenide superconductors A2Fe4Se5 （A=K, Cs, T1- K, Rb, T1-Rb） （245） compounds, with Tc ～30K, have attracted much interest A high transition- temperature （TN ≈ 470-560K） and large magnetic moment （3.3μB/Fe） block antiferromagnetic （AFM） order exists in the superconducting samples. Mag- netic order-parameter experiences an anomaly when Tc is approached. The superconductors crystal- lize with a highly ordered √5 × √5 superstructure, in which the Fel site of the I4/m structure is only a few percents occupied and the Fe2 site is fully occupied. The non-superconducting samples at low-T also crystallize in the I4/m structure, while both Fe sites are fractionally occupied, since the numbers of the Fe vacancies in the samples and the vacant sites in the √5 × √5 pattern are mismatched. The partially ordered √5× √5 vacancy order becomes one of three competing phases for temperature below room temperature up to ～ 500K, namely, these sam- ples are phase-separated and in the miscibility gap 1lacier the n,mhi^nt condition.展开更多
The magnetic structure of the spin-chain antiferromagnet SrCo2 V208 is determined by single-crystal neutron diffraction experiment. The system undergoes a long-range magnetic order below the critical temperature TN=4....The magnetic structure of the spin-chain antiferromagnet SrCo2 V208 is determined by single-crystal neutron diffraction experiment. The system undergoes a long-range magnetic order below the critical temperature TN=4.96 K. The moment of 2.16#B per Co at 1.6K in the screw chain running along the c axis Mternates in the c axis. The moments of neighboring screw chains are arranged antiferromagnetically along one in-plane axis and ferromagnetieally Monk the other in-plane axis. This magnetic configuration breaks the four-fold symmetry of the tetragonM crystal structure and leads to two equally populated magnetic twins with the antiferromagnetic vector in the a or b axis. The very similar magnetic state to the isostructural BaCo2 V~ 08 warrants SrCo2 V2 08 as another interesting half-integer spin-chain antiferromagnet for investigation on quantum antiferromagnetism.展开更多
The magnetic structure of CsCo_2 Se_2 was investigated using single-crystal neutron diffraction technique. An antiferromagnetic transition with the propagation vector（0,0,1） was observed at TN= 78 K. The Co magnetic...The magnetic structure of CsCo_2 Se_2 was investigated using single-crystal neutron diffraction technique. An antiferromagnetic transition with the propagation vector（0,0,1） was observed at TN= 78 K. The Co magnetic moment 0.772（6） μB at 10 K pointing in the basal plane couples ferromagnetically in the plane, which stacks antiferromagnetically along the c direction. Tuning and suppressing the interplane antiferromagnetic interaction may be crucial to induce a superconducting state in the material.展开更多
In a Dirac semimetal, the massless Dirac fermion has zero chirality, leading to surface states connected adiabatically to a topologically trivial surface state as well as vanishing anomalous Hall effect. Recently, it ...In a Dirac semimetal, the massless Dirac fermion has zero chirality, leading to surface states connected adiabatically to a topologically trivial surface state as well as vanishing anomalous Hall effect. Recently, it is predicted that in the nonrelativistic limit of certain collinear antiferromagnets, there exists a type of chiral“Dirac-like” fermion, whose dispersion manifests four-fold degenerate crossing points formed by spin-degenerate linear bands, with topologically protected Fermi arcs. Such an unconventional chiral fermion, protected by a hidden SU(2) symmetry in the hierarchy of an enhanced crystallographic group, namely spin space group, is not experimentally verified yet. Here, by angle-resolved photoemission spectroscopy measurements, we reveal the surface origin of the electron pocket at the Fermi surface in collinear antiferromagnet CoNb3S6. Combining with neutron diffraction and first-principles calculations, we suggest a multidomain collinear antiferromagnetic configuration, rendering the the existence of the Fermi-arc surface states induced by chiral Dirac-like fermions.Our work provides spectral evidence of the chiral Dirac-like fermion caused by particular spin symmetry in CoNb_(3)S_(6), paving an avenue for exploring new emergent phenomena in antiferromagnets with unconventional quasiparticle excitations.展开更多
基金The work at SUSTech was supported by the National Natural Science Foundation of China(Grant No.11974157)Part of this work was also supported by the National Natural Science Foundation of China(Grant No.11875265)+1 种基金the Scientific Instrument Developing Project of the Chinese Academy of Sciences(3He-based neutron polarization devices)the Institute of High Energy Physics,the Chinese Academy of Sciences.Kan X C and Tian M L were supported by the National Natural Science Foundation of China(Grant No.51802002).
文摘The magnetic phase diagram of rare-earth perovskite compound,GdScO3,has been investigated by magnetization and heat capacity.The system undergoes an antiferromagnetic phase transition at TN=2.6 K,with an easy axis of magnetization along the a axis.The magnetization measurements show that it exists a spin-flop transition around 0.3 T for the applied field along the a axis.The critical magnetic field for the antiferromagnetic-to-paramagnetic transition is near 3.2 T when temperature approaches zero.By scaling susceptibilities,we presume this point(B=3.2 T,T=0 K)might be a fieldinduced quantum critical point and the magnetic critical fluctuations can even be felt above TN.
基金Supported by the National Basic Research Program of China under Grant Nos 2012CB921700, 2011CBA00112, 2011CBA00103 and 2012CB821404, the National Natural Science Foundation of China under Grant Nos 11034012, 11190024, 11374261 and 11204059, the Natural Science Foundation of Zhejiang Province under Grant No LQI2A04007, and the Scientific User Facilities Division of the Office of Basic Energy Sciences of U.S. DOE.
文摘The recently discovered metal-intercalated iron selenide superconductors A2Fe4Se5 （A=K, Cs, T1- K, Rb, T1-Rb） （245） compounds, with Tc ～30K, have attracted much interest A high transition- temperature （TN ≈ 470-560K） and large magnetic moment （3.3μB/Fe） block antiferromagnetic （AFM） order exists in the superconducting samples. Mag- netic order-parameter experiences an anomaly when Tc is approached. The superconductors crystal- lize with a highly ordered √5 × √5 superstructure, in which the Fel site of the I4/m structure is only a few percents occupied and the Fe2 site is fully occupied. The non-superconducting samples at low-T also crystallize in the I4/m structure, while both Fe sites are fractionally occupied, since the numbers of the Fe vacancies in the samples and the vacant sites in the √5 × √5 pattern are mismatched. The partially ordered √5× √5 vacancy order becomes one of three competing phases for temperature below room temperature up to ～ 500K, namely, these sam- ples are phase-separated and in the miscibility gap 1lacier the n,mhi^nt condition.
基金Supported by the National Basic Research Program of China under Grant Nos 2012CB921700 and 2011CBA00112the National Natural Science Foundation of China under Grant Nos 11034012 and 11190024
文摘The magnetic structure of the spin-chain antiferromagnet SrCo2 V208 is determined by single-crystal neutron diffraction experiment. The system undergoes a long-range magnetic order below the critical temperature TN=4.96 K. The moment of 2.16#B per Co at 1.6K in the screw chain running along the c axis Mternates in the c axis. The moments of neighboring screw chains are arranged antiferromagnetically along one in-plane axis and ferromagnetieally Monk the other in-plane axis. This magnetic configuration breaks the four-fold symmetry of the tetragonM crystal structure and leads to two equally populated magnetic twins with the antiferromagnetic vector in the a or b axis. The very similar magnetic state to the isostructural BaCo2 V~ 08 warrants SrCo2 V2 08 as another interesting half-integer spin-chain antiferromagnet for investigation on quantum antiferromagnetism.
基金Project supported by the National Basic Research Program of China(Grant No.2012CB921700)the National Natural Science Foundation of China(Grant No.11190024)+2 种基金the Fundamental Research Funds for the Central Universities,Chinathe Research Funds of Renmin University of China(Grant Nos.17XNLF04 and 17XNLF06)support from China Scholarship Council
文摘The magnetic structure of CsCo_2 Se_2 was investigated using single-crystal neutron diffraction technique. An antiferromagnetic transition with the propagation vector（0,0,1） was observed at TN= 78 K. The Co magnetic moment 0.772（6） μB at 10 K pointing in the basal plane couples ferromagnetically in the plane, which stacks antiferromagnetically along the c direction. Tuning and suppressing the interplane antiferromagnetic interaction may be crucial to induce a superconducting state in the material.
基金supported by the National Key R&D Program of China (Grant Nos. 2020YFA0308900 and 2022YFA1403700)the National Natural Science Foundation of China (Grant Nos. 12074163, 12134020, 11974157, 12104255, 12004159, and 12374146)+8 种基金Guangdong Provincial Key Laboratory for Computational Science and Material Design (Grant No. 2019B030301001)the Science, Technology and Innovation Commission of Shenzhen Municipality (Grant Nos. ZDSYS20190902092905285 and KQTD20190929173815000)Guangdong Basic and Applied Basic Research Foundation (Grant Nos. 2022B1515020046, 2021B1515130007, 2022A1515011915, 2019A1515110712, and 2022B1515130005)Shenzhen Science and Technology Program (Grant Nos. RCJC20221008092722009 and RCBS20210706092218039)the Guangdong Innovative and Entrepreneurial Research Team Program (Grant No. 2019ZT08C044)the beam time awarded by Australia’s Nuclear Science and Technology Organisation (ANSTO) (Grant No. P8130)the Materials and Life Science Experimental Facility of the Japan Proton Accelerator Research Complex (J-PARC) was performed under a user program (Proposal No. 2019B0140)performed at the Hiroshima Synchrotron Radiation Center (HiSOR) of Japan (Grant Nos. 22BG023 and 22BG029)Shanghai Synchrotron Radiation Facility (SSRF) BL03U (Grant No. 2022-SSRF-PT-020848)。
文摘In a Dirac semimetal, the massless Dirac fermion has zero chirality, leading to surface states connected adiabatically to a topologically trivial surface state as well as vanishing anomalous Hall effect. Recently, it is predicted that in the nonrelativistic limit of certain collinear antiferromagnets, there exists a type of chiral“Dirac-like” fermion, whose dispersion manifests four-fold degenerate crossing points formed by spin-degenerate linear bands, with topologically protected Fermi arcs. Such an unconventional chiral fermion, protected by a hidden SU(2) symmetry in the hierarchy of an enhanced crystallographic group, namely spin space group, is not experimentally verified yet. Here, by angle-resolved photoemission spectroscopy measurements, we reveal the surface origin of the electron pocket at the Fermi surface in collinear antiferromagnet CoNb3S6. Combining with neutron diffraction and first-principles calculations, we suggest a multidomain collinear antiferromagnetic configuration, rendering the the existence of the Fermi-arc surface states induced by chiral Dirac-like fermions.Our work provides spectral evidence of the chiral Dirac-like fermion caused by particular spin symmetry in CoNb_(3)S_(6), paving an avenue for exploring new emergent phenomena in antiferromagnets with unconventional quasiparticle excitations.
