Spin-wave excitation plays important roles in the investigation of the magnetic phases. In this paper, we study the spin-wave excitation spectra of two-component Bose gases with spin-orbit coupling in a deep square op...Spin-wave excitation plays important roles in the investigation of the magnetic phases. In this paper, we study the spin-wave excitation spectra of two-component Bose gases with spin-orbit coupling in a deep square optical lattice using the spin-wave theory. We find that, while the excitation spectrum of the vortex crystal phase is gapless with a linear dispersion in the vicinity of the minimum point, the spectra of the commensurate spiral spin phase and the skyrmion crystal phase are gapped. Significantly, the spin fluctuations strongly destabilize the classical ground state of the skyrmion phase with the appearance of an imaginary part in the eigenfrequencies of spin excitations. Such features of the spin excitation spectra provide further insights into the exotic spin phases.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
We report a new kagome quantum spin liquid candidate CuaZn(OH)6FBr, which does not experience any phase transition down to 50inK, more than three orders lower than the antiferromagnetic Curie-Weiss temperature (-20...We report a new kagome quantum spin liquid candidate CuaZn(OH)6FBr, which does not experience any phase transition down to 50inK, more than three orders lower than the antiferromagnetic Curie-Weiss temperature (-200 K). A clear gap opening at low temperature is observed in the uniform spin susceptibility obtained from 19F nuclear magnetic resonance measurements. We observe the characteristic magnetic field dependence of the gap as expected for fractionalized spin-1/2 spinon excitations. Our experimental results provide firm evidence for spin fractionalization in a topologically ordered spin system, resembling charge fraetionalization in the fractional quantum Hall state.展开更多
The magnetization curves at 1.5 K and thermomagnetic curves for amorphous Fe_(90-x)Si_xZr_(10)(x=0,4,7 and 10)alloys prepared by the drum spinning technique have been measured with an extracting sample magnetometer.It...The magnetization curves at 1.5 K and thermomagnetic curves for amorphous Fe_(90-x)Si_xZr_(10)(x=0,4,7 and 10)alloys prepared by the drum spinning technique have been measured with an extracting sample magnetometer.It is obtained that the average magnetic moment,,per magnetic atom and Curie temperature,T_c,in the amorphous FeSiZr alloys increase with increasing Si content.The and T_c are found to be quite small,compared with amorphous FeSiB alloys.This unusual behavior is suggested to be due to the presence of the Fe—Fe antiferromagnetic interactions.The temperature dependence of magnetization at lower temperature is in accordance with Bloch's T^(3/2) law.Calculation shows that the spin wave stiffness constant,D,increases with increasing Si content from 0.37 meV·nm^2 for x=0 to 0.538 meV·nm^2 for x=10.The values of<r^2>indicate that the range of the exchange interaction is roughly the mean atomic distance of nearest neighbours.展开更多
We report our nuclear magnetic resonance(NMR) study on the structurally spin chain compound Ni_(2)NbBO_(6) with complex magnetic coupling.The antiferromagnetic transition is monitored by the line splitting resulting f...We report our nuclear magnetic resonance(NMR) study on the structurally spin chain compound Ni_(2)NbBO_(6) with complex magnetic coupling.The antiferromagnetic transition is monitored by the line splitting resulting from the staggered internal hyperfine field.The magnetic coupling configuration proposed by the first-principle density functional theory(DFT) is supported by NMR spectral analysis.For the spin dynamics,a prominent peak at T~35 K well above the Neel temperature(T_(N)~20 K at μ0 H=10 T) is observed from the spin-lattice relaxation data.As compared with the dc-susceptibility,this behavior indicates an antiferromagnetic coupling with the typical energy scale of ~3 meV.Thus,the Ni_(2)NbBO_(6) compound can be viewed as strongly ferromagnetically coupled armchair spin chains along the crystalline b-axis.These facts place strong constraints on the theoretical model for this compound.展开更多
We studied the system of pure Rashba spin–orbit coupled Bose gas with an in-plane magnetic field. Based on the mean field theory, we obtained the zero temperature phase diagram of the system which exhibits three phas...We studied the system of pure Rashba spin–orbit coupled Bose gas with an in-plane magnetic field. Based on the mean field theory, we obtained the zero temperature phase diagram of the system which exhibits three phases, plane wave(PW) phase, striped wave(SW) phase, and zero momentum(ZM) phase. It was shown that with a growing in-plane field,both SW and ZM phases will eventually turn into the PW phase. Furthermore, we adopted the Bogoliubov theory to study the excitation spectrum as well as the sound speed.展开更多
We report scanning tunneling microscopy/spectroscopy(STM/STS) studies on iron-based superconductors of Ba1-xKxFe2As2 and nearly optimally doped Fe(Te,Se). Mode-like features were observed universally outside the s...We report scanning tunneling microscopy/spectroscopy(STM/STS) studies on iron-based superconductors of Ba1-xKxFe2As2 and nearly optimally doped Fe(Te,Se). Mode-like features were observed universally outside the superconducting gaps in the tunneling spectra, which are similar to our previous observations in other samples and can be ascribed to the interaction between electrons and spin excitations. Furthermore, an almost linear relationship between the superconducting gaps and the superconducting transition temperatures was noted and should also be taken into account in understanding the mechanism of iron-based superconductors.展开更多
Spin properties of organic molecules have attracted great interest for their potential applications in spintronic devices and quantum computing.Fe-tetraphenyl porphyrin(Fe TPP)is of particular interest for its robust ...Spin properties of organic molecules have attracted great interest for their potential applications in spintronic devices and quantum computing.Fe-tetraphenyl porphyrin(Fe TPP)is of particular interest for its robust magnetic properties on metallic substrates.Fe TPP is prepared in vacuum via on-surface synthesis.Molecular structure and spin-related transport properties are characterized by low-temperature scanning tunneling microscope and spectroscopy at 0.5 K.Density functional theory calculations are performed to understand molecular adsorption and spin distribution on Au(111).The molecular structure of Fe TPP is distorted upon adsorption on the substrate.Spin excitations of Fe TPP are observed on the Fe atom and high pyrrole groups in differential conductance spectra.The calculated spin density distribution indicates that the electron spin of Fe TPP is mainly distributed on the Fe atom.The atomic transmission calculation indicates that electrons transport to substrate is mediated through Fe atom,when the tip is above the high pyrrole group.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.11347197,11404225,and 11474205)
文摘Spin-wave excitation plays important roles in the investigation of the magnetic phases. In this paper, we study the spin-wave excitation spectra of two-component Bose gases with spin-orbit coupling in a deep square optical lattice using the spin-wave theory. We find that, while the excitation spectrum of the vortex crystal phase is gapless with a linear dispersion in the vicinity of the minimum point, the spectra of the commensurate spiral spin phase and the skyrmion crystal phase are gapped. Significantly, the spin fluctuations strongly destabilize the classical ground state of the skyrmion phase with the appearance of an imaginary part in the eigenfrequencies of spin excitations. Such features of the spin excitation spectra provide further insights into the exotic spin phases.
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Supported by the National Key Research and Development Program of China under Grant Nos 2016YFA0300502,2016YFA0300503,2016YFA0300604,2016YF0300300 and 2016YFA0300802the National Natural Science Foundation of China under Grant Nos 11421092,11474330,11574359,11674406,11374346 and 11674375+3 种基金the National Basic Research Program of China(973 Program)under Grant No 2015CB921304the National Thousand-Young-Talents Program of Chinathe Strategic Priority Research Program(B) of the Chinese Academy of Sciences under Grant Nos XDB07020000,XDB07020200 and XDB07020300supported by DOE-BES under Grant No DE-FG02-04ER46148
文摘We report a new kagome quantum spin liquid candidate CuaZn(OH)6FBr, which does not experience any phase transition down to 50inK, more than three orders lower than the antiferromagnetic Curie-Weiss temperature (-200 K). A clear gap opening at low temperature is observed in the uniform spin susceptibility obtained from 19F nuclear magnetic resonance measurements. We observe the characteristic magnetic field dependence of the gap as expected for fractionalized spin-1/2 spinon excitations. Our experimental results provide firm evidence for spin fractionalization in a topologically ordered spin system, resembling charge fraetionalization in the fractional quantum Hall state.
文摘The magnetization curves at 1.5 K and thermomagnetic curves for amorphous Fe_(90-x)Si_xZr_(10)(x=0,4,7 and 10)alloys prepared by the drum spinning technique have been measured with an extracting sample magnetometer.It is obtained that the average magnetic moment,,per magnetic atom and Curie temperature,T_c,in the amorphous FeSiZr alloys increase with increasing Si content.The and T_c are found to be quite small,compared with amorphous FeSiB alloys.This unusual behavior is suggested to be due to the presence of the Fe—Fe antiferromagnetic interactions.The temperature dependence of magnetization at lower temperature is in accordance with Bloch's T^(3/2) law.Calculation shows that the spin wave stiffness constant,D,increases with increasing Si content from 0.37 meV·nm^2 for x=0 to 0.538 meV·nm^2 for x=10.The values of<r^2>indicate that the range of the exchange interaction is roughly the mean atomic distance of nearest neighbours.
基金Project supported by the National Key Research and Development Program of China(Grant No.2016YFA0401802)the National Natural Science Foundation of China(Grant Nos.11874057,11504377,11574288,11874158,U1732273,and 21927814)+1 种基金the Users with Excellence Program of Hefei Science Center CAS(Grant No.2019HSC-UE008)supported by the High Magnetic Field Laboratory of Anhui Province。
文摘We report our nuclear magnetic resonance(NMR) study on the structurally spin chain compound Ni_(2)NbBO_(6) with complex magnetic coupling.The antiferromagnetic transition is monitored by the line splitting resulting from the staggered internal hyperfine field.The magnetic coupling configuration proposed by the first-principle density functional theory(DFT) is supported by NMR spectral analysis.For the spin dynamics,a prominent peak at T~35 K well above the Neel temperature(T_(N)~20 K at μ0 H=10 T) is observed from the spin-lattice relaxation data.As compared with the dc-susceptibility,this behavior indicates an antiferromagnetic coupling with the typical energy scale of ~3 meV.Thus,the Ni_(2)NbBO_(6) compound can be viewed as strongly ferromagnetically coupled armchair spin chains along the crystalline b-axis.These facts place strong constraints on the theoretical model for this compound.
基金Project supported by the National Natural Science Foundation of China(Grant No.10774088)
文摘We studied the system of pure Rashba spin–orbit coupled Bose gas with an in-plane magnetic field. Based on the mean field theory, we obtained the zero temperature phase diagram of the system which exhibits three phases, plane wave(PW) phase, striped wave(SW) phase, and zero momentum(ZM) phase. It was shown that with a growing in-plane field,both SW and ZM phases will eventually turn into the PW phase. Furthermore, we adopted the Bogoliubov theory to study the excitation spectrum as well as the sound speed.
基金supported by the National Basic Research Program of China(Grant Nos.2011CBA00110 and 2012CB821403)the National Natural Science Foundation of China(Grant Nos.11174349 and 11322432)the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant No.XDB07020300)
文摘We report scanning tunneling microscopy/spectroscopy(STM/STS) studies on iron-based superconductors of Ba1-xKxFe2As2 and nearly optimally doped Fe(Te,Se). Mode-like features were observed universally outside the superconducting gaps in the tunneling spectra, which are similar to our previous observations in other samples and can be ascribed to the interaction between electrons and spin excitations. Furthermore, an almost linear relationship between the superconducting gaps and the superconducting transition temperatures was noted and should also be taken into account in understanding the mechanism of iron-based superconductors.
基金supported by the Ministry of Science and Technology(Nos.2017YFA0205003,2018YFA0306003)National Natural Science Foundation of China(Nos.21991132,21972002,21902003,21673118,21972067)。
文摘Spin properties of organic molecules have attracted great interest for their potential applications in spintronic devices and quantum computing.Fe-tetraphenyl porphyrin(Fe TPP)is of particular interest for its robust magnetic properties on metallic substrates.Fe TPP is prepared in vacuum via on-surface synthesis.Molecular structure and spin-related transport properties are characterized by low-temperature scanning tunneling microscope and spectroscopy at 0.5 K.Density functional theory calculations are performed to understand molecular adsorption and spin distribution on Au(111).The molecular structure of Fe TPP is distorted upon adsorption on the substrate.Spin excitations of Fe TPP are observed on the Fe atom and high pyrrole groups in differential conductance spectra.The calculated spin density distribution indicates that the electron spin of Fe TPP is mainly distributed on the Fe atom.The atomic transmission calculation indicates that electrons transport to substrate is mediated through Fe atom,when the tip is above the high pyrrole group.