Quasi-one-dimensional(1D)antiferromagnets are known to display intriguing phenomena especially when there is a spin gap in their spin-excitation spectra.Here we demonstrate that a spin gap exists in the quasi-1D Heise...Quasi-one-dimensional(1D)antiferromagnets are known to display intriguing phenomena especially when there is a spin gap in their spin-excitation spectra.Here we demonstrate that a spin gap exists in the quasi-1D Heisenberg antiferromagnet CoTi2O5 with highly ordered Co2+/Ti4+occupation,in which the Co2+ions with S=3/2 form a 1D spin chain along the a-axis.CoTi2O5 undergoes an antiferromagnetic transition at TN~24 K and exhibits obvious anisotropic magnetic susceptibility even in the paramagnetic region.Although a gapless magnetic ground state is usually expected in a quasi-1D Heisenberg antiferromagnet with half-integer spins,by analyzing the specific heat,the thermal conductivity,and the spin-lattice relaxation rate(1/T1)as a function of temperature,we found that a spin gap is opened in the spin-excitation spectrum of CoTi2O5 around TN,manifested by the rapid decrease of magnetic specific heat to zero,the double-peak characteristic in thermal conductivity,and the exponential decay of 1/T1 below TN.Both the magnetic measurements and the first-principles calculations results indicate that there is spin-orbit coupling in CoTi2O5,which induces the magnetic anisotropy in CoTi2O5,and then opens the spin gap at low temperature.展开更多
A biosensor featuring an S-tapered fiber(STF) with a composite bio-sensitive film comprising graphene oxide and gold nanoparticles, has been proposed for the rapid, highly sensitive, and label-free detection of pseudo...A biosensor featuring an S-tapered fiber(STF) with a composite bio-sensitive film comprising graphene oxide and gold nanoparticles, has been proposed for the rapid, highly sensitive, and label-free detection of pseudomonas exotoxin(PE).The STF was created using a fusion splicer. Subsequently, the composite film and nanobody were successively assembled onto its surface. The detection mechanism relies on monitoring changes in the external refractive index induced by the specific binding of PE to the nanobody. The developed STF biosensor exhibited a remarkable sensitivity of 0.28 nm/(ng/mL)and a limit of detection as low as 0.21 ng/mL for PE.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 52372003)the Funds from Beijing National Laboratory for Condensed Matter Physics
文摘Quasi-one-dimensional(1D)antiferromagnets are known to display intriguing phenomena especially when there is a spin gap in their spin-excitation spectra.Here we demonstrate that a spin gap exists in the quasi-1D Heisenberg antiferromagnet CoTi2O5 with highly ordered Co2+/Ti4+occupation,in which the Co2+ions with S=3/2 form a 1D spin chain along the a-axis.CoTi2O5 undergoes an antiferromagnetic transition at TN~24 K and exhibits obvious anisotropic magnetic susceptibility even in the paramagnetic region.Although a gapless magnetic ground state is usually expected in a quasi-1D Heisenberg antiferromagnet with half-integer spins,by analyzing the specific heat,the thermal conductivity,and the spin-lattice relaxation rate(1/T1)as a function of temperature,we found that a spin gap is opened in the spin-excitation spectrum of CoTi2O5 around TN,manifested by the rapid decrease of magnetic specific heat to zero,the double-peak characteristic in thermal conductivity,and the exponential decay of 1/T1 below TN.Both the magnetic measurements and the first-principles calculations results indicate that there is spin-orbit coupling in CoTi2O5,which induces the magnetic anisotropy in CoTi2O5,and then opens the spin gap at low temperature.
基金supported by the National Natural Science Foundation of China (Nos.91860140,62090064,and U19A2077)。
文摘A biosensor featuring an S-tapered fiber(STF) with a composite bio-sensitive film comprising graphene oxide and gold nanoparticles, has been proposed for the rapid, highly sensitive, and label-free detection of pseudomonas exotoxin(PE).The STF was created using a fusion splicer. Subsequently, the composite film and nanobody were successively assembled onto its surface. The detection mechanism relies on monitoring changes in the external refractive index induced by the specific binding of PE to the nanobody. The developed STF biosensor exhibited a remarkable sensitivity of 0.28 nm/(ng/mL)and a limit of detection as low as 0.21 ng/mL for PE.
