Thermally activated flux flow, vortex-glass phase transition and the mixed-state Hall effect in 112-type iron pnictide superconductors

• Published in: Science China. Physics, mechanics & astronomy mechanics & astronomy, 2018-12, Vol.61 (12), p.127406, Article 127406
• Main Authors: Xing, XiangZhuo, Li, ZhanFeng, Yi, XiaoLei, Feng, JiaJia, Xu, ChunQiang, Zhou, Nan, Meng, Yan, Zhang, YuFeng, Pan, YongQiang, Qin, LingYao, Zhou, Wei, Zhao, HaiJun, Shi, ZhiXiang
• Format: Article
• Language: English
• Subjects: Activation energy; Astronomy; Classical and Continuum Physics; Cuprates; Electric properties; Electrical resistivity; Electromagnetism; Fluid dynamics; Fluid flow; Group 5A compounds; Hall effect; Iron; Laws, regulations and rules; Magnetic fields; Observations and Techniques; Phase diagrams; Phase transitions; Physics; Physics and Astronomy; Single crystals; Superconductors; Transport properties; Vortices
• ISSN: 1674-7348; 1869-1927
• DOI: 10.1007/s11433-018-9280-6

The transport properties in the mixed state of high-quality Ca 0.8 La 0.2 Fe 0.98 Co 0.02 As 2 single crystal, a newly discovered 112-type iron pnictide superconductor, are comprehensively studied by magneto-resistivity measurement. The field-dependent activation energy, U 0 , is derived in the framework of thermally activated flux flow (TAFF) theory, yielding a power law dependence U 0 ~ H α with a crossover at a magnetic field around 2 T in both H ⊥ ab and H // ab , which is ascribed to the different pinning mechanisms. Moreover, we have clearly observed the vortex phase transition from vortex-glass to vortex-liquid according to the vortex-glass model, and vortex phase diagrams are constructed for both H ⊥ ab and H // ab . Finally, the results of mixed-state Hall effect show that no sign reversal of transverse resistivity ρ xy ( H ) is detected, indicating that the Hall component arising from the vortex flow is also negative based on the time dependent Ginzburg-Landau (TDGL) theory. Meanwhile, the transverse resistivity ρ xy ( H ) and the longitudinal resistivity ρ xx ( H ) follow the relation | ρ xy ( H )|= Aρ xx ( H ) β well with an exponent β ~2.0, which is in line with the results in theories or experiments previously reported on some high- T c cuprates.