We develop superconducting quantum interference device(SQUID)probes based on 3D nano-bridge junctions for the scanning SQUID microscopy.The use of these nano-bridge junctions enables imaging in the presence of a high ...We develop superconducting quantum interference device(SQUID)probes based on 3D nano-bridge junctions for the scanning SQUID microscopy.The use of these nano-bridge junctions enables imaging in the presence of a high magnetic field.Conventionally,a superconducting ground layer has been employed for better magnetic shielding.In our study,we prepare a number of scanning SQUID probes with and without a ground layer to evaluate their performance in external magnetic fields.The devices show the improved magnetic modulation up to 1.4 T.It is found that the ground layer reduces the inductance,and increases the modulation depth and symmetricity of the gradiometer design in the absence of the field.However,the layer is not compatible with the use of the scanning SQUID probe in the field because it decreases its working field range.Moreover,by adding the layer,the mutual inductance between the feedback coil and the SQUID also decreases linearly as a function of the field.展开更多
FeTe, a non-superconducting parent compound in the iron-chalcogenide family, becomes superconducting after annealing in oxygen. Under the presence of magnetism, spin-orbit coupling, inhomogeneity and lattice distortio...FeTe, a non-superconducting parent compound in the iron-chalcogenide family, becomes superconducting after annealing in oxygen. Under the presence of magnetism, spin-orbit coupling, inhomogeneity and lattice distortion,the nature of its superconductivity is not well understood. Here we combine the mutual inductance technique with magneto transport to study the magnetization and superconductivity of FeTe thin films. It is found that the films with the highest TC show non-saturating superfluid density and a strong magnetic hysteresis distinct from that in a homogeneous superconductor. Such a hysteresis can be well explained by a two-level critical state model and suggests the importance of granularity to superconductivity in this compound.展开更多
We report the Meissner effect studies on an Fe Se thin film grown on Nb-doped Sr Ti O3 substrate by molecular beam epitaxy. Two-coil mutual inductance measurement clearly demonstrates the onset of diamagnetic screenin...We report the Meissner effect studies on an Fe Se thin film grown on Nb-doped Sr Ti O3 substrate by molecular beam epitaxy. Two-coil mutual inductance measurement clearly demonstrates the onset of diamagnetic screening at 65 K, which is consistent with the gap opening temperature determined by previous angle-resolved photoemission spectroscopy results. The applied magnetic field causes a broadening of the superconducting transition near the onset temperature, which is the typical behavior for quasi-two-dimensional superconductors. Our results provide direct evidence that Fe Se thin film grown on Nb-doped Sr Ti O3 substrate has an onset TC* 65 K,which is the highest among all iron-based superconductors discovered so far.展开更多
基金Supported by the National Key R&D Program of China(Grant Nos.2017YFF0206105,2016YFA0301002 and 2017YFA0303000)the Young Investigator Program of CAS(Grant No.2016217)+3 种基金the Frontier Science Key Programs of the CAS(Grant No.QYZDY-SSW-JSC033)the Strategic Priority Research Program of CAS(Grant No.XDA18000000)the Shanghai Municipal Science and Technology Major Project(Grant No.2019SHZDZX01)the National Natural Science Foundation of China(Grant No.11827805).
文摘We develop superconducting quantum interference device(SQUID)probes based on 3D nano-bridge junctions for the scanning SQUID microscopy.The use of these nano-bridge junctions enables imaging in the presence of a high magnetic field.Conventionally,a superconducting ground layer has been employed for better magnetic shielding.In our study,we prepare a number of scanning SQUID probes with and without a ground layer to evaluate their performance in external magnetic fields.The devices show the improved magnetic modulation up to 1.4 T.It is found that the ground layer reduces the inductance,and increases the modulation depth and symmetricity of the gradiometer design in the absence of the field.However,the layer is not compatible with the use of the scanning SQUID probe in the field because it decreases its working field range.Moreover,by adding the layer,the mutual inductance between the feedback coil and the SQUID also decreases linearly as a function of the field.
基金Supported by the National Key Research and Development Program of China under Grant Nos 2016YFA0301002 and 2017YFA0303000the National Natural Science Foundation of China under Grant No 11827805
文摘FeTe, a non-superconducting parent compound in the iron-chalcogenide family, becomes superconducting after annealing in oxygen. Under the presence of magnetism, spin-orbit coupling, inhomogeneity and lattice distortion,the nature of its superconductivity is not well understood. Here we combine the mutual inductance technique with magneto transport to study the magnetization and superconductivity of FeTe thin films. It is found that the films with the highest TC show non-saturating superfluid density and a strong magnetic hysteresis distinct from that in a homogeneous superconductor. Such a hysteresis can be well explained by a two-level critical state model and suggests the importance of granularity to superconductivity in this compound.
基金supported by the National Natural Science Foundation and Ministry of Science and Technology of China(2015CB921000 and 2012CB921402)Yihua Wang is partially supported by the Urbanek Fellowship of the Department of Applied Physics at Stanford UniversityK.A.Moler is supported by the Department of Energy,Office of Science,Basic Energy Sciences,Materials Sciences and Engineering Division,under Contract DEAC02-76SF00515
文摘We report the Meissner effect studies on an Fe Se thin film grown on Nb-doped Sr Ti O3 substrate by molecular beam epitaxy. Two-coil mutual inductance measurement clearly demonstrates the onset of diamagnetic screening at 65 K, which is consistent with the gap opening temperature determined by previous angle-resolved photoemission spectroscopy results. The applied magnetic field causes a broadening of the superconducting transition near the onset temperature, which is the typical behavior for quasi-two-dimensional superconductors. Our results provide direct evidence that Fe Se thin film grown on Nb-doped Sr Ti O3 substrate has an onset TC* 65 K,which is the highest among all iron-based superconductors discovered so far.
