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Two-band and pauli-limiting effects on the upper critical field of 112-type iron pnictide superconductors

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ABSTRACT

The temperature dependence of upper critical field μ0Hc2 of Ca0.83La0.17FeAs2 and Ca0.8La0.2Fe0.98Co0.02As2 single crystals are investigated by measuring the resistivity for the inter-plane (H//c) and in-plane (H//ab) directions in magnetic fields up to 60 T. It is found that μ0Hc2(T) of both crystals for H//c presents a sublinear temperature dependence with decreasing temperature, whereas the curve of μ0Hc2(T) for H//ab has a convex curvature and gradually tends to saturate at low temperatures. μ0Hc2(T) in both crystals deviates from the conventional Werthamer-Helfand-Hohenberg (WHH) theoretical model without considering spin paramagnetic effect for H//c and H//ab directions. Detailed analyses show that the behavior of μ0Hc2(T) in 112-type Iron-based superconductors (IBSs) is similar to that of most IBSs. Two-band model is required to fully reproduce the behavior of μ0Hc2(T) for H//c, while the effect of spin paramagnetic effect is responsible for the behavior of μ0Hc2(T) for H//ab.

No MeSH data available.


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Temperature dependence of the in-plane electrical resistivity ρ(T) for (a) Ca0.83La0.17FeAs2 and (b) Ca0.8La0.2Fe0.98Co0.02As2 single crystals at zero field. The insets of (a) and (b) show an enlarged view of resistivity near the superconducting transition, Tc was determind by the 50% normal state resistivity ρn.
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f1: Temperature dependence of the in-plane electrical resistivity ρ(T) for (a) Ca0.83La0.17FeAs2 and (b) Ca0.8La0.2Fe0.98Co0.02As2 single crystals at zero field. The insets of (a) and (b) show an enlarged view of resistivity near the superconducting transition, Tc was determind by the 50% normal state resistivity ρn.

Mentions: Figure 1 presents the temperature dependence of the in-plane resistivity ρ(T) at zero field for (a) Ca0.83La0.17FeAs2 and (b) Ca0.8La0.2Fe0.98Co0.02As2 single crystals. The resistivity of both crystals monotonically decreases with decreasing temperature and shows no anomaly corresponding to the antiferromagnetic (AFM)/structural transition down to Tc. The insets show the enlarged view near the superconducting transition. The transition temperature is estimated as  = 40.8 K for Ca0.83La0.17FeAs2 and  = 38.8 K for Ca0.8La0.2Fe0.98Co0.02As2. The transition width ΔTc, determined by adopting the criterion of 90%ρn–10%ρn, is 3.8 K for Ca0.83La0.17FeAs2, larger than the value of 1.1 K for Ca0.8La0.2Fe0.98Co0.02As2. The slightly wide superconducting transition for Ca0.83La0.17FeAs2 seems to be a general feature in this compound, which may result from the inhomogeneity of La distribution. Upon a small amount of Co doping, single crystal quality can be improved significantly with sharp superconducting transition and large superconducting volume fraction20212223.


Two-band and pauli-limiting effects on the upper critical field of 112-type iron pnictide superconductors
Temperature dependence of the in-plane electrical resistivity ρ(T) for (a) Ca0.83La0.17FeAs2 and (b) Ca0.8La0.2Fe0.98Co0.02As2 single crystals at zero field. The insets of (a) and (b) show an enlarged view of resistivity near the superconducting transition, Tc was determind by the 50% normal state resistivity ρn.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5382916&req=5

f1: Temperature dependence of the in-plane electrical resistivity ρ(T) for (a) Ca0.83La0.17FeAs2 and (b) Ca0.8La0.2Fe0.98Co0.02As2 single crystals at zero field. The insets of (a) and (b) show an enlarged view of resistivity near the superconducting transition, Tc was determind by the 50% normal state resistivity ρn.
Mentions: Figure 1 presents the temperature dependence of the in-plane resistivity ρ(T) at zero field for (a) Ca0.83La0.17FeAs2 and (b) Ca0.8La0.2Fe0.98Co0.02As2 single crystals. The resistivity of both crystals monotonically decreases with decreasing temperature and shows no anomaly corresponding to the antiferromagnetic (AFM)/structural transition down to Tc. The insets show the enlarged view near the superconducting transition. The transition temperature is estimated as  = 40.8 K for Ca0.83La0.17FeAs2 and  = 38.8 K for Ca0.8La0.2Fe0.98Co0.02As2. The transition width ΔTc, determined by adopting the criterion of 90%ρn–10%ρn, is 3.8 K for Ca0.83La0.17FeAs2, larger than the value of 1.1 K for Ca0.8La0.2Fe0.98Co0.02As2. The slightly wide superconducting transition for Ca0.83La0.17FeAs2 seems to be a general feature in this compound, which may result from the inhomogeneity of La distribution. Upon a small amount of Co doping, single crystal quality can be improved significantly with sharp superconducting transition and large superconducting volume fraction20212223.

View Article: PubMed Central - PubMed

ABSTRACT

The temperature dependence of upper critical field μ0Hc2 of Ca0.83La0.17FeAs2 and Ca0.8La0.2Fe0.98Co0.02As2 single crystals are investigated by measuring the resistivity for the inter-plane (H//c) and in-plane (H//ab) directions in magnetic fields up to 60 T. It is found that μ0Hc2(T) of both crystals for H//c presents a sublinear temperature dependence with decreasing temperature, whereas the curve of μ0Hc2(T) for H//ab has a convex curvature and gradually tends to saturate at low temperatures. μ0Hc2(T) in both crystals deviates from the conventional Werthamer-Helfand-Hohenberg (WHH) theoretical model without considering spin paramagnetic effect for H//c and H//ab directions. Detailed analyses show that the behavior of μ0Hc2(T) in 112-type Iron-based superconductors (IBSs) is similar to that of most IBSs. Two-band model is required to fully reproduce the behavior of μ0Hc2(T) for H//c, while the effect of spin paramagnetic effect is responsible for the behavior of μ0Hc2(T) for H//ab.

No MeSH data available.


Related in: MedlinePlus