Modulated electronic state due to the layered crystal structures brings about moderate anisotropy of superconductivity in the iron-based superconductors and thus Abrikosov vortices are expected in the mixed state.Howe...Modulated electronic state due to the layered crystal structures brings about moderate anisotropy of superconductivity in the iron-based superconductors and thus Abrikosov vortices are expected in the mixed state.However,based on the angular and temperature dependent transport measurements in iron-based superconductor Ca_(10)(Pt_(3)As_(8))((Fe_(0.9)Pt_(0.1))_(2)As_(2))_(5) with Tc(≌)12 K,we find clear evidences of a crossover from Abrikosov vortices to Josephson vortices at a crossover temperature T*(≌)7 K,when the applied magnetic field is parallel to the superconducting FeAs layers,i.e.,the angle between the magnetic field and the FeAs layers θ=0°.This crossover to Josephson vortices is demonstrated by an abnormal decrease(increase)of the critical current(flux-flow resistance)below T*,in contrast to the increase(decrease)of the critical current(flux-flow resistance)above T* expected for Abrikosov vortices.Furthermore,when θ is larger than 0.5°,the flux-flow resistance and critical current have no anomalous behaviors across T*.These anomalous behaviors can be understood in terms of the distinct transition from the well-pinned Abrikosov vortices to the weakly-pinned Josephson vortices upon cooling,when the coherent length perpendicular to the FeAs layers ξ⊥ becomes shorter than half of the interlayer distance d/2.These experimental findings indicate the existence of intrinsic Josephson junctions below T* and thus quasi-two-dimensional superconductivity in Ca10(Pt3As8)((Fe0.9Pt0.1)2As2)5,similar to those in the cuprate superconductors.展开更多
Electrodynamic phenomena related to vortices in superconductors have been studied since their prediction by Abrikosov, and seem to hold no fundamental mysteries. However, most of the effects are treated separately, wi...Electrodynamic phenomena related to vortices in superconductors have been studied since their prediction by Abrikosov, and seem to hold no fundamental mysteries. However, most of the effects are treated separately, with no guiding principles. We demonstrate that the relativistic vortex worldsheet in spacetime is the object that naturally conveys all electric and magnetic information, for which we obtain simple and concise equations. Breaking Lorentz invariance leads to down-to-earth Abrikosov vortices, and special limits of these equations include for instance dynamic Meissner screening and the AC Josephson relation. On a deeper level, we explore the electrodynamics of two-form sources in the absence of electric monopoles, in which the electromagnetic field strength itself acquires the characteristics of a gauge field. This novel framework leaves room for unexpected surprises .展开更多
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFA0302903)the National Natural Science Foundation of China(Grant No.11974412).
文摘Modulated electronic state due to the layered crystal structures brings about moderate anisotropy of superconductivity in the iron-based superconductors and thus Abrikosov vortices are expected in the mixed state.However,based on the angular and temperature dependent transport measurements in iron-based superconductor Ca_(10)(Pt_(3)As_(8))((Fe_(0.9)Pt_(0.1))_(2)As_(2))_(5) with Tc(≌)12 K,we find clear evidences of a crossover from Abrikosov vortices to Josephson vortices at a crossover temperature T*(≌)7 K,when the applied magnetic field is parallel to the superconducting FeAs layers,i.e.,the angle between the magnetic field and the FeAs layers θ=0°.This crossover to Josephson vortices is demonstrated by an abnormal decrease(increase)of the critical current(flux-flow resistance)below T*,in contrast to the increase(decrease)of the critical current(flux-flow resistance)above T* expected for Abrikosov vortices.Furthermore,when θ is larger than 0.5°,the flux-flow resistance and critical current have no anomalous behaviors across T*.These anomalous behaviors can be understood in terms of the distinct transition from the well-pinned Abrikosov vortices to the weakly-pinned Josephson vortices upon cooling,when the coherent length perpendicular to the FeAs layers ξ⊥ becomes shorter than half of the interlayer distance d/2.These experimental findings indicate the existence of intrinsic Josephson junctions below T* and thus quasi-two-dimensional superconductivity in Ca10(Pt3As8)((Fe0.9Pt0.1)2As2)5,similar to those in the cuprate superconductors.
文摘Electrodynamic phenomena related to vortices in superconductors have been studied since their prediction by Abrikosov, and seem to hold no fundamental mysteries. However, most of the effects are treated separately, with no guiding principles. We demonstrate that the relativistic vortex worldsheet in spacetime is the object that naturally conveys all electric and magnetic information, for which we obtain simple and concise equations. Breaking Lorentz invariance leads to down-to-earth Abrikosov vortices, and special limits of these equations include for instance dynamic Meissner screening and the AC Josephson relation. On a deeper level, we explore the electrodynamics of two-form sources in the absence of electric monopoles, in which the electromagnetic field strength itself acquires the characteristics of a gauge field. This novel framework leaves room for unexpected surprises .
