Thioacetamide is made from phosphorus pentasulfide and acetamide,which react with(3aS,6aR)-1,3-dibenzyl-hexahydro-1H-furo[3,4-d]imidazole-2,4-dione as sulfo-reagent to prepare(3aS,6aR)-1,3-dibenzyl-hexahydro-1H-thieno...Thioacetamide is made from phosphorus pentasulfide and acetamide,which react with(3aS,6aR)-1,3-dibenzyl-hexahydro-1H-furo[3,4-d]imidazole-2,4-dione as sulfo-reagent to prepare(3aS,6aR)-1,3-dibenzyl-hexahydro-1H-thienoimidazole-2,4-dione in the same system,yield is 91.9%,material get easily and cost reduce by this method,which is suitable for industrial process.展开更多
We predict that the recently discovered quasi-one-dimensional superconductors, A2 Cr3As3 （A=K, Rb）, possess strong frustrated magnetic fluctuations and are nearby a novel in-out co-planar magnetic ground state. The ...We predict that the recently discovered quasi-one-dimensional superconductors, A2 Cr3As3 （A=K, Rb）, possess strong frustrated magnetic fluctuations and are nearby a novel in-out co-planar magnetic ground state. The frustrated magnetism is very sensitive to the c-axis lattice constant and can thus be suppressed by increasing pressure. Our results qualitatively explain strong non-Fermi liquid behaviors observed in the normal state of the superconductors as the intertwining between the magnetism and superconductivity can create a large quantum critical region in quasi-one-dimensional systems and also suggest that the materials share similar phase diagrams and superconducting mechanism with other unconventional superconductors, such as cuprates and iron-based superconductors.展开更多
The Mn doping effects on the gate-tunable transport properties of topological Dirac semimetal Cd3As2 films have been investigated.Mn-doped Cd3As2 films are directly grown on GaAs(111)B substrates by molecular-beam epi...The Mn doping effects on the gate-tunable transport properties of topological Dirac semimetal Cd3As2 films have been investigated.Mn-doped Cd3As2 films are directly grown on GaAs(111)B substrates by molecular-beam epitaxy,during which the single crystal phase can be obtained with Mn concentration less than 2%.Shubnikov-de Haas oscillation and quantum Hall effect are observed at low temperatures,and electrons are found to be the dominant carrier in the whole temperature range.Higher Mn content results in smaller lattice constant,lower electron mobility and larger effective band gap,while the carrier density seems to be unaffected by Mn-doping.Gating experiments show that Shubnikov-de Haas oscillation and quantum Hall effect are slightly modulated by electric field,which can be explained by the variation of electron density.Our results provide useful information for understanding the magnetic element doping effects on the transport properties of Cd3As2 films.展开更多
Ultrafast optical spectroscopy of a single crystal of a Dirac semimetal Cd_3As_（2 ）is carried out.An acoustic phonon（AP）mode with central frequency f=0.037 THz（i.e.,1.23 cm^（-1）or 0.153 meV）is unambiguously ge...Ultrafast optical spectroscopy of a single crystal of a Dirac semimetal Cd_3As_（2 ）is carried out.An acoustic phonon（AP）mode with central frequency f=0.037 THz（i.e.,1.23 cm^（-1）or 0.153 meV）is unambiguously generated and detected,which we attribute to laser-induced thermal strain.An AP chirping（i.e.,variation of the phonon frequency）is clearly detected,which is ascribed to heat capacity variation with time.By comparing our experimental results and the theoretical model,we obtain a chirping time constant,which is 31.2 ps at 6 K and 19.8 ps at 300 K,respectively.Significantly,we identify an asymmetry in the AP frequency domain peak and find that it is caused by the chirping,instead of a Fano resonance.Moreover,we experimentally demonstrate that the central frequency of AP is extremely stable with varying laser fluence,as well as temperature,which endows Cd_3As_2application potentials in thermoelectric devices.展开更多
We report 75As-nuclear magnetic resonance(NMR)and nuclear quadrupole resonance(NQR)measurements on transition-metal arsenides LaRu2As2,KCa2Fe4As4F2,and A2Cr3As3.In the superconducting state of LaRu2As2,a Hebel–Slicht...We report 75As-nuclear magnetic resonance(NMR)and nuclear quadrupole resonance(NQR)measurements on transition-metal arsenides LaRu2As2,KCa2Fe4As4F2,and A2Cr3As3.In the superconducting state of LaRu2As2,a Hebel–Slichter coherence peak is found in the temperature dependence of the spin-lattice relaxation rate 1/T1 just below Tc,which indicates that LaRu2As2 is a full-gap superperconducor.For KCa2Fe4As4F2,antiferromagnetic spin fluctuations are observed in the normal state.We further find that the anisotropy rate RAF=Tc 1/Tab 1 is small and temperature independent,implying that the low energy spin fluctuations are isotropic in spin space.Our results indicate that KCa2Fe4As4F2 is a moderately overdoped iron-arsenide high-temperature superconductor with a stoichiometric composition.For A2Cr3As3(A=Na,K,Rb,Cs),we calculate the electric field gradient by first-principle method and assign the 75As-NQR peaks to two crystallographically different As sites,paving the way for further NMR investigation.展开更多
文摘Thioacetamide is made from phosphorus pentasulfide and acetamide,which react with(3aS,6aR)-1,3-dibenzyl-hexahydro-1H-furo[3,4-d]imidazole-2,4-dione as sulfo-reagent to prepare(3aS,6aR)-1,3-dibenzyl-hexahydro-1H-thienoimidazole-2,4-dione in the same system,yield is 91.9%,material get easily and cost reduce by this method,which is suitable for industrial process.
基金Supported by the National Basic Research Program of China under Grant Nos 2010CB922904,2012CV821400 and2015CB921300the National Natural Science Foundation of China under Grant Nos 1190024,11175248 and 11104339the Strategic Priority Research Program of Chinese Academy of Sciences under Grant No XDB07000000
文摘We predict that the recently discovered quasi-one-dimensional superconductors, A2 Cr3As3 （A=K, Rb）, possess strong frustrated magnetic fluctuations and are nearby a novel in-out co-planar magnetic ground state. The frustrated magnetism is very sensitive to the c-axis lattice constant and can thus be suppressed by increasing pressure. Our results qualitatively explain strong non-Fermi liquid behaviors observed in the normal state of the superconductors as the intertwining between the magnetism and superconductivity can create a large quantum critical region in quasi-one-dimensional systems and also suggest that the materials share similar phase diagrams and superconducting mechanism with other unconventional superconductors, such as cuprates and iron-based superconductors.
基金supported by NSFC(Grants Nos.U1632264 and 11704374)the the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant Nos.XDB44000000 and QYZDY-SSW-JSC015)。
文摘The Mn doping effects on the gate-tunable transport properties of topological Dirac semimetal Cd3As2 films have been investigated.Mn-doped Cd3As2 films are directly grown on GaAs(111)B substrates by molecular-beam epitaxy,during which the single crystal phase can be obtained with Mn concentration less than 2%.Shubnikov-de Haas oscillation and quantum Hall effect are observed at low temperatures,and electrons are found to be the dominant carrier in the whole temperature range.Higher Mn content results in smaller lattice constant,lower electron mobility and larger effective band gap,while the carrier density seems to be unaffected by Mn-doping.Gating experiments show that Shubnikov-de Haas oscillation and quantum Hall effect are slightly modulated by electric field,which can be explained by the variation of electron density.Our results provide useful information for understanding the magnetic element doping effects on the transport properties of Cd3As2 films.
基金Supported by the National Key Research and Development Program of China under Grant Nos 2017YFA0303603,2016YFA0300303,2017YFA0302901 and 2016YFA0300604the National Natural Science Foundation of China under Grant Nos11774408,11574383 and 11774399+1 种基金the External Cooperation Program of Chinese Academy of Sciences under Grant No GJHZ1826the Interdisciplinary Innovation Team of Chinese Academy of Sciences
文摘Ultrafast optical spectroscopy of a single crystal of a Dirac semimetal Cd_3As_（2 ）is carried out.An acoustic phonon（AP）mode with central frequency f=0.037 THz（i.e.,1.23 cm^（-1）or 0.153 meV）is unambiguously generated and detected,which we attribute to laser-induced thermal strain.An AP chirping（i.e.,variation of the phonon frequency）is clearly detected,which is ascribed to heat capacity variation with time.By comparing our experimental results and the theoretical model,we obtain a chirping time constant,which is 31.2 ps at 6 K and 19.8 ps at 300 K,respectively.Significantly,we identify an asymmetry in the AP frequency domain peak and find that it is caused by the chirping,instead of a Fano resonance.Moreover,we experimentally demonstrate that the central frequency of AP is extremely stable with varying laser fluence,as well as temperature,which endows Cd_3As_2application potentials in thermoelectric devices.
基金National Natural Science Foundation of China(Grant Nos.11674377,11634015,and 11974405)the National Key R&D Program of China(Grant Nos.2017YFA0302904 and 2016YFA0300502)J.Y.also acknowledges support by the Youth Innovation Promotion Association of Chinese Academy of Sciences.
文摘We report 75As-nuclear magnetic resonance(NMR)and nuclear quadrupole resonance(NQR)measurements on transition-metal arsenides LaRu2As2,KCa2Fe4As4F2,and A2Cr3As3.In the superconducting state of LaRu2As2,a Hebel–Slichter coherence peak is found in the temperature dependence of the spin-lattice relaxation rate 1/T1 just below Tc,which indicates that LaRu2As2 is a full-gap superperconducor.For KCa2Fe4As4F2,antiferromagnetic spin fluctuations are observed in the normal state.We further find that the anisotropy rate RAF=Tc 1/Tab 1 is small and temperature independent,implying that the low energy spin fluctuations are isotropic in spin space.Our results indicate that KCa2Fe4As4F2 is a moderately overdoped iron-arsenide high-temperature superconductor with a stoichiometric composition.For A2Cr3As3(A=Na,K,Rb,Cs),we calculate the electric field gradient by first-principle method and assign the 75As-NQR peaks to two crystallographically different As sites,paving the way for further NMR investigation.
