The modulation of topological electronic state by an external magnetic field is highly desired for condensed-matter physics.Schemes to achieve this have been proposed theoretically,but few can be realized experimental...The modulation of topological electronic state by an external magnetic field is highly desired for condensed-matter physics.Schemes to achieve this have been proposed theoretically,but few can be realized experimentally.Here,combining transverse transport,theoretical calculations,and scanning tunneling microscopy/spectroscopy(STM/S)investigations,we provide an observation that the topological electronic state,accompanied by an emergent magneto-transport phenomenon,was modulated by applying magnetic field through induced non-collinear magnetism in the magnetic Weyl semimetal EuB6.A giant unconventional anomalous Hall effect(UAHE)is found during the magnetization re-orientation from easy axes to hard ones in magnetic field,with a UAHE peak around the low field of 5 kOe.展开更多
Recent studies have shown that layered compound EuCd_(2)As_(2) could exhibit diverse topological states depending on the different magnetic structures,such as Weyl semimetal,Dirac semimetal and topological insulato r....Recent studies have shown that layered compound EuCd_(2)As_(2) could exhibit diverse topological states depending on the different magnetic structures,such as Weyl semimetal,Dirac semimetal and topological insulato r.In order to further study the interplay between magnetism and topology of EuCd_(2)As_(2),it is necessary to figure out its magnetic structure.Here,by magnetization(M) measurements and negative magnetostriction(λ) along the [001] direction measured by scanning tunneling microscopy on EuCd_(2)As_(2) single crystals,we observe field-induced metamagnetic phase transition from A-type antiferromagnetic(AFM) ground state to field-polarized state,with canted AFM(CAFM) state in between.Magnetization and magnetostriction are more sensitive to the in-plane field than the out-of-plane field,indicating the magnetic moments lying in the ab plane.The absence of abrupt jump on M-H and λ-H curves demonstrates that the phase transition is a second-order type.In CAFM state,M increases linearly with the field and λ is proportional to M~2.Tunneling conductance spectra show the field-induced evolution of the electronic density of states.Our results provide experimental evidence for understanding the magnetic structure of EuCd_(2)As_(2).展开更多
We report a comprehensive neutron scattering study on the spin excitations in the magnetic Weyl semimetal Co3Sn2S2 with a quasi-two-dimensional structure.Both in-plane and out-of-plane dispersions of the spin waves we...We report a comprehensive neutron scattering study on the spin excitations in the magnetic Weyl semimetal Co3Sn2S2 with a quasi-two-dimensional structure.Both in-plane and out-of-plane dispersions of the spin waves were revealed in the ferromagnetic state.Similarly,dispersive but damped spin excitations were found in the paramagnetic state.The effective exchange interactions were estimated using a semi-classical Heisenberg model to consistently reproduce the experimental TCand spin stiffness.However,a full spin wave gap below Eg=2.3 meV was observed at T=4 K.This value was considerably larger than the estimated magnetic anisotropy energy(~0.6 meV),and its temperature dependence indicated a significant contribution from the Weyl fermions.These results suggest that Co3Sn2S2 is a three-dimensional correlated system with a large spin stiffness,and the low-energy spin dynamics can interplay with the topological electron states.展开更多
Based on the first-principles calculations and experimental measurements,we report that the hexagonal phase of ternary transition metal pnictides TT’X(T=Zr,Hf;T’=Ru;X=P,As),which are well-known noncentrosymmetric su...Based on the first-principles calculations and experimental measurements,we report that the hexagonal phase of ternary transition metal pnictides TT’X(T=Zr,Hf;T’=Ru;X=P,As),which are well-known noncentrosymmetric superconductors with relatively high transition temperatures,host nontrivial bulk topology.Before the superconducting phase transition,we find that HfRuP belongs to a Weyl semimetal phase with 12 pairs of type-II Weyl points,while ZrRuAs,ZrRuP and HfRuAs belong to a topological crystalline insulating phase with trivial Fu-Kane Z_(2) indices but nontrivial mirror Chern numbers.High-quality single crystal samples of the noncentrosymmetric superconductors with these two different topological states have been obtained and the superconductivity is verified experimentally.The wide-range band structures of ZrRuAs have been identified by ARPES and reproduced by theoretical calculations.Combined with intrinsic superconductivity,the nontrivial topology of the normal state may generate unconventional superconductivity in both bulk and surfaces.Our findings could largely inspire the experimental searching for possible topological superconductivity in these compounds.展开更多
Co_(3)Sn_(2)S_(2) is a recently identified magnetic Weyl semimetal in Shandite compounds. Upon cooling, Co_(3)Sn_(2)S_(2) undergoes a ferromagnetic transition with c-axis polarized moments(0.3 μ_(B)/Co) around T_(C)=...Co_(3)Sn_(2)S_(2) is a recently identified magnetic Weyl semimetal in Shandite compounds. Upon cooling, Co_(3)Sn_(2)S_(2) undergoes a ferromagnetic transition with c-axis polarized moments(0.3 μ_(B)/Co) around T_(C)= 175 K, followed by another magnetic anomaly around T_(A)≈ 140 K. A large intrinsic anomalous Hall effect is observed in the magnetic state below TC with a maximum of anomalous Hall angle near T_(A). Here, we report an elastic neutron scattering on the crystalline lattice of Co_(3)Sn_(2)S_(2) in a magnetic field up to 10 T. A strongly anisotropic magnetoelastic response is observed, while only a slight enhancement of the Bragg peaks is observed when B//c. The in-plane magnetic field(B//ab) dramatically suppresses the Bragg peak intensity probably by tilting the moments and lattice toward the external field direction. The in-plane magnetoelastic response commences from T_(C), and as it is further strengthened below T_(A), it becomes nonmonotonic against the field between T_(A) and T_(C) because of the competition from another in-plane magnetic order. These results suggest that a magnetic field can be employed to tune the Co_(3)Sn_(2)S_(2) lattice and its related topological states.展开更多
A study on anomalous nuclear fusion reaction by using lOkV pulsed high voltage discharge in deuterium was completed,During high voltage(HV)pulses no neutron signal was detected,but two peaks of gamma rays were detecte...A study on anomalous nuclear fusion reaction by using lOkV pulsed high voltage discharge in deuterium was completed,During high voltage(HV)pulses no neutron signal was detected,but two peaks of gamma rays were detected.The energies of two gamma rays are at 425 and 870keV,respectively.It might be explained as^(108)Pd^(*)and^(56)Fe^(*) excited by high energy charged particles de-exciting radiations.Neither neutron signal nor gamma signal was detected in the intervals between the pulses.展开更多
We report the physical properties, crystalline and magnetic structures of singe crystals of a new layered antiferromagnetic(AFM) material PrPd0.82Bi2. The measurements of magnetic properties and heat capacity indicate...We report the physical properties, crystalline and magnetic structures of singe crystals of a new layered antiferromagnetic(AFM) material PrPd0.82Bi2. The measurements of magnetic properties and heat capacity indicate an AFM phase transition at TN^7K. A large Sommerfeld coefficient of 329.23 m J·mol-1·K-2 is estimated based on the heat capacity data, implying a possible heavy-fermion behavior. The magnetic structure of this compound is investigated by a combined study of neutron powder and single-crystal diffraction. It is found that an A-type AFM structure with magnetic propagation wavevector k =(0 0 0) is formed below TN. The Pr3+ magnetic moment is aligned along the crystallographic c-axis with an ordered moment of 1.694(3) μBat 4K, which is smaller than the effective moment of the free Pr3+ ion of 3.58 μB.PrPd0.82Bi2 can be grown as large as 1 mm×1 cm in area with a layered shape, and is very easy to be cleaved, providing a unique opportunity to study the interplay between magnetism, possible heavy fermions, and superconductivity.展开更多
基金supported by the National Key R&D Program of China(nos.2022YFA1403800,2022YFA1403400,2019YFA0704900)the Fundamental Science Center of the National Natural Science Foundation of China(no.52088101)+7 种基金the Synergetic Extreme Condition User Facility(SECUF)the Beijing Natural Science Foundation(no.Z190009)the National Natural Science Foundation of China(nos.11974394,12174426,12104280,and 12004416)the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(CAS)(XDB33000000)the Key Research Program of CAS(no.ZDRW-CN-2021-3)the CAS Project for Young Scientists in Basic Research(YSBR-003)the Scientific Instrument Developing Project of CAS(no.ZDKYYQ20210003)the Basic Research Plan of Shanxi Province(no.20210302124160).
文摘The modulation of topological electronic state by an external magnetic field is highly desired for condensed-matter physics.Schemes to achieve this have been proposed theoretically,but few can be realized experimentally.Here,combining transverse transport,theoretical calculations,and scanning tunneling microscopy/spectroscopy(STM/S)investigations,we provide an observation that the topological electronic state,accompanied by an emergent magneto-transport phenomenon,was modulated by applying magnetic field through induced non-collinear magnetism in the magnetic Weyl semimetal EuB6.A giant unconventional anomalous Hall effect(UAHE)is found during the magnetization re-orientation from easy axes to hard ones in magnetic field,with a UAHE peak around the low field of 5 kOe.
基金Project supported by the National Natural Science Foundation of China(11227903,12004416,U2032204)the Beijing Municipal Science and Technology Commission(Z181100004218007,Z191100007219011)+3 种基金the National Basic Research Program of China(2015CB921304)the National Key Research and Development Program of China(2017YFA0302903,2016YFJC010282,2016YFA0300602,2016YFA0300604)the Strategic Priority Research Program of Chinese Academy of Sciences(XDB07000000,XDB28000000,XDB33000000)。
文摘Recent studies have shown that layered compound EuCd_(2)As_(2) could exhibit diverse topological states depending on the different magnetic structures,such as Weyl semimetal,Dirac semimetal and topological insulato r.In order to further study the interplay between magnetism and topology of EuCd_(2)As_(2),it is necessary to figure out its magnetic structure.Here,by magnetization(M) measurements and negative magnetostriction(λ) along the [001] direction measured by scanning tunneling microscopy on EuCd_(2)As_(2) single crystals,we observe field-induced metamagnetic phase transition from A-type antiferromagnetic(AFM) ground state to field-polarized state,with canted AFM(CAFM) state in between.Magnetization and magnetostriction are more sensitive to the in-plane field than the out-of-plane field,indicating the magnetic moments lying in the ab plane.The absence of abrupt jump on M-H and λ-H curves demonstrates that the phase transition is a second-order type.In CAFM state,M increases linearly with the field and λ is proportional to M~2.Tunneling conductance spectra show the field-induced evolution of the electronic density of states.Our results provide experimental evidence for understanding the magnetic structure of EuCd_(2)As_(2).
基金supported by the National Key Research and Development Program of China(Grant Nos.2017YFA0303100,2017YFA0302900,2016YFA0300500,2017YFA0206300,and 2019YFA0704900)the National Natural Science Foundation of China(Grant Nos.11974392,11974394,11822411,51722106,11674372,11774399,11961160699,and 12061130200)+3 种基金the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(CAS)(Grant Nos.XDB07020300,XDB25000000,and XDB33000000)the Beijing Natural Science Foundation(Grant Nos.JQ19002,Z180008,and Z190009)support from the Youth Innovation Promotion Association of CAS(Grant Nos.2013002,and 2016004)support from the K.C.Wong Education Foundation(GJTD-2018-01)。
文摘We report a comprehensive neutron scattering study on the spin excitations in the magnetic Weyl semimetal Co3Sn2S2 with a quasi-two-dimensional structure.Both in-plane and out-of-plane dispersions of the spin waves were revealed in the ferromagnetic state.Similarly,dispersive but damped spin excitations were found in the paramagnetic state.The effective exchange interactions were estimated using a semi-classical Heisenberg model to consistently reproduce the experimental TCand spin stiffness.However,a full spin wave gap below Eg=2.3 meV was observed at T=4 K.This value was considerably larger than the estimated magnetic anisotropy energy(~0.6 meV),and its temperature dependence indicated a significant contribution from the Weyl fermions.These results suggest that Co3Sn2S2 is a three-dimensional correlated system with a large spin stiffness,and the low-energy spin dynamics can interplay with the topological electron states.
基金This work was supported by the National Natural Science Foundation of China(11504117,11774399,11622435,U1832202)Beijing Natural Science Foundation(Z180008)+6 种基金the Ministry of Science and Technology of China(2016YFA0300600,2016YFA0401000 and 2018YFA0305700)the Chinese Academy of Sciences(XDB28000000,XDB07000000)the Beijing Municipal Science and Technology Commission(Z181100004218001,Z171100002017018)H.W.acknowledges support from the Science Challenge Project(No.TZ2016004)the K.C.Wong Education Foundation(GJTD-2018-01)Y.S.acknowledges the National Key Research and Development Program of China(No.2017YFA0302901)Z.W.acknowledges support from the National Thousand-Young-Talents Program and the CAS Pioneer Hundred Talents Program.
文摘Based on the first-principles calculations and experimental measurements,we report that the hexagonal phase of ternary transition metal pnictides TT’X(T=Zr,Hf;T’=Ru;X=P,As),which are well-known noncentrosymmetric superconductors with relatively high transition temperatures,host nontrivial bulk topology.Before the superconducting phase transition,we find that HfRuP belongs to a Weyl semimetal phase with 12 pairs of type-II Weyl points,while ZrRuAs,ZrRuP and HfRuAs belong to a topological crystalline insulating phase with trivial Fu-Kane Z_(2) indices but nontrivial mirror Chern numbers.High-quality single crystal samples of the noncentrosymmetric superconductors with these two different topological states have been obtained and the superconductivity is verified experimentally.The wide-range band structures of ZrRuAs have been identified by ARPES and reproduced by theoretical calculations.Combined with intrinsic superconductivity,the nontrivial topology of the normal state may generate unconventional superconductivity in both bulk and surfaces.Our findings could largely inspire the experimental searching for possible topological superconductivity in these compounds.
基金supported by the National Key Research and Development Program of China(Grant Nos.2017YFA0303100,2017YFA0302900,2016YFA0300500,and 2017YFA0206300)the National Natural Science Foundation of China(Grant Nos.11974392,11974394,11822411,51722106,11674372,11774399,11961160699,and 12061130200)+2 种基金the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(CAS)(Grant Nos.XDB07020300,XDB25000000,and XDB33000000)the Beijing Natural Science Foundation(Grant Nos.JQ19002,Z180008,and Z190009)the support from the Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant Nos.2013002,and 2016004)。
文摘Co_(3)Sn_(2)S_(2) is a recently identified magnetic Weyl semimetal in Shandite compounds. Upon cooling, Co_(3)Sn_(2)S_(2) undergoes a ferromagnetic transition with c-axis polarized moments(0.3 μ_(B)/Co) around T_(C)= 175 K, followed by another magnetic anomaly around T_(A)≈ 140 K. A large intrinsic anomalous Hall effect is observed in the magnetic state below TC with a maximum of anomalous Hall angle near T_(A). Here, we report an elastic neutron scattering on the crystalline lattice of Co_(3)Sn_(2)S_(2) in a magnetic field up to 10 T. A strongly anisotropic magnetoelastic response is observed, while only a slight enhancement of the Bragg peaks is observed when B//c. The in-plane magnetic field(B//ab) dramatically suppresses the Bragg peak intensity probably by tilting the moments and lattice toward the external field direction. The in-plane magnetoelastic response commences from T_(C), and as it is further strengthened below T_(A), it becomes nonmonotonic against the field between T_(A) and T_(C) because of the competition from another in-plane magnetic order. These results suggest that a magnetic field can be employed to tune the Co_(3)Sn_(2)S_(2) lattice and its related topological states.
文摘A study on anomalous nuclear fusion reaction by using lOkV pulsed high voltage discharge in deuterium was completed,During high voltage(HV)pulses no neutron signal was detected,but two peaks of gamma rays were detected.The energies of two gamma rays are at 425 and 870keV,respectively.It might be explained as^(108)Pd^(*)and^(56)Fe^(*) excited by high energy charged particles de-exciting radiations.Neither neutron signal nor gamma signal was detected in the intervals between the pulses.
基金National Key Research and Development Program of China(Grant Nos.2017YFA0302901 and 2016YFA0300604)the National Natural Science Foundation of China(Grant No.11774399)+2 种基金Beijing Natural Science Foundation,China(Grant No.Z180008)the K.C.Wong Education Foundation(Grant No.GJTD-2018-01)the DAAD-PPP programme,and the joint German-Sino HGF-OCPC Postdoc Programme.
文摘We report the physical properties, crystalline and magnetic structures of singe crystals of a new layered antiferromagnetic(AFM) material PrPd0.82Bi2. The measurements of magnetic properties and heat capacity indicate an AFM phase transition at TN^7K. A large Sommerfeld coefficient of 329.23 m J·mol-1·K-2 is estimated based on the heat capacity data, implying a possible heavy-fermion behavior. The magnetic structure of this compound is investigated by a combined study of neutron powder and single-crystal diffraction. It is found that an A-type AFM structure with magnetic propagation wavevector k =(0 0 0) is formed below TN. The Pr3+ magnetic moment is aligned along the crystallographic c-axis with an ordered moment of 1.694(3) μBat 4K, which is smaller than the effective moment of the free Pr3+ ion of 3.58 μB.PrPd0.82Bi2 can be grown as large as 1 mm×1 cm in area with a layered shape, and is very easy to be cleaved, providing a unique opportunity to study the interplay between magnetism, possible heavy fermions, and superconductivity.
