Abstract
We investigate the relation of the critical current density (Jc) and the remarkably increased superconducting transition temperature (Tc) for the FeSe single crystals under pressures up to 2.43 GPa, where the Tc is increased by ~8 K/GPa. The critical current density corresponding to the free flux flow is monotonically enhanced by pressure which is due to the increase in Tc, whereas the depinning critical current density at which the vortex starts to move is more influenced by the pressure-induced magnetic state compared to the increase of Tc. Unlike other high-Tc superconductors, FeSe is not magnetic, but superconducting at ambient pressure. Above a critical pressure where magnetic state is induced and coexists with superconductivity, the depinning Jc abruptly increases even though the increase of the zero-resistivity Tc is negligible, directly indicating that the flux pinning property compared to the Tc enhancement is a more crucial factor for an achievement of a large Jc. In addition, the sharp increase in Jc in the coexisting superconducting phase of FeSe demonstrates that vortices can be effectively trapped by the competing antiferromagnetic order, even though its antagonistic nature against superconductivity is well documented. These results provide new guidance toward technological applications of high-temperature superconductors.
Highlights
Flux lines have a normal state within the core, they tend to be pinned at defects where superconductivity is suppressed, i.e., extrinsic pinning effects
We report the evolution of the critical current density (Jc) of FeSe single crystals as a function of pressure in connection with the increase of Tc
Correlation between the anomalous broadening in the Δ Tc and the magnetic phase is further supported by a qualitative difference in the current-voltage (I−V) curves of FeSe across the critical pressure Pc
Summary
Flux lines have a normal state within the core, they tend to be pinned at defects where superconductivity is suppressed, i.e., extrinsic pinning effects Another possible approach to improve the Jc is associated with an intrinsic property of materials, e.g., a coexisting order with superconductivity as an intrinsic pinning source. Several high-Tc superconductors, such as La2−xSrxCuO4 and Ba(Fe1−xCox)2As2, are candidate materials for the intrinsic pinning because superconductivity occurs in the vicinity of an antiferromagnetically ordered state[6,7,8]. The binary high-Tc superconductor FeSe is a promising candidate to probe the effects of the intrinsic pinning and the Tc on the Jc, because superconductivity which appears at ~10 K without introducing a hole or electron in the parent compound is greatly tunable up to 37 K by application of pressure[12,13]. The fact that physical pressure does not induce extra disorder suggests that the enhancement in Jc as well as the change in the pinning mechanism in the coexisting phase arises from the antiferromagnetically ordered state
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
