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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.


The anisotropic parameter γ versus the reduced temperature T/Tc for Ca0.83La0.17FeAs2 (red circles) and Ca0.8La0.2Fe0.98Co0.02As2 (blue circles) single crystals.
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f5: The anisotropic parameter γ versus the reduced temperature T/Tc for Ca0.83La0.17FeAs2 (red circles) and Ca0.8La0.2Fe0.98Co0.02As2 (blue circles) single crystals.

Mentions: The temperature dependence of anisotropy of μ0Hc2(T) is shown in Fig. 5 as a function of reduced temperature t = T/Tc for Ca0.83La0.17FeAs2 and Ca0.8La0.2Fe0.98Co0.02As2 single crystals. The values of γ reside in the range 1.2~3.2 (2.3 – 5.4) for Ca0.83La0.17FeAs2 (Ca0.8La0.2Fe0.98Co0.02As2) in the temperature region of T = (0.51 ~ 1) Tc. The anisotropy γ values of both crystals show nonmonotonic temperature-dependent, which first increase and then decrease with decreasing temperature, in consistence with our earlier studies23. This strong temperature dependence of γ is similar to that of SmFeAs(O, F), which may originate from the combined effect of two-band nature and spin paramagnetism10. The decreasing γ with decreasing temperature in both crystals results from the enhanced μ0Hc2,c(T) and the suppressed μ0Hc2,ab(T).


Two-band and pauli-limiting effects on the upper critical field of 112-type iron pnictide superconductors
The anisotropic parameter γ versus the reduced temperature T/Tc for Ca0.83La0.17FeAs2 (red circles) and Ca0.8La0.2Fe0.98Co0.02As2 (blue circles) single crystals.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f5: The anisotropic parameter γ versus the reduced temperature T/Tc for Ca0.83La0.17FeAs2 (red circles) and Ca0.8La0.2Fe0.98Co0.02As2 (blue circles) single crystals.
Mentions: The temperature dependence of anisotropy of μ0Hc2(T) is shown in Fig. 5 as a function of reduced temperature t = T/Tc for Ca0.83La0.17FeAs2 and Ca0.8La0.2Fe0.98Co0.02As2 single crystals. The values of γ reside in the range 1.2~3.2 (2.3 – 5.4) for Ca0.83La0.17FeAs2 (Ca0.8La0.2Fe0.98Co0.02As2) in the temperature region of T = (0.51 ~ 1) Tc. The anisotropy γ values of both crystals show nonmonotonic temperature-dependent, which first increase and then decrease with decreasing temperature, in consistence with our earlier studies23. This strong temperature dependence of γ is similar to that of SmFeAs(O, F), which may originate from the combined effect of two-band nature and spin paramagnetism10. The decreasing γ with decreasing temperature in both crystals results from the enhanced μ0Hc2,c(T) and the suppressed μ0Hc2,ab(T).

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.