Microwave surface impedance measurements of LiFeAs, LiFe(As,P) and FeSe sub(1-x)Te sub(x) single crystals

We study microwave surface impedance measurements of LiFeAs, LiFe(As,P) and FeSe sub(1-x)Te sub(x) single crystals. The in-plane penetration depths of LiFeAs and LiFe(As,P) depend on temperature exponentially at low temperatures, which is a strong indication that these two materials have the nodeles...

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Bibliographic Details
Published in:Physica. C, Superconductivity Superconductivity, 2011-11, Vol.471 (21-22), p.630-633
Main Authors: Imai, Y, Takahashi, H, Okada, T, Yoshinaka, T, Komiya, S, Kitagawa, K, Matsubayashi, K, Tsukada, I, Uwatoko, Y, Maeda, A
Format: Article
Language:English
Subjects:
Density
Fluids
Impedance measurement
Microwaves
Penetration depth
Single crystals
Superconductivity
Temperature dependence
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Summary:We study microwave surface impedance measurements of LiFeAs, LiFe(As,P) and FeSe sub(1-x)Te sub(x) single crystals. The in-plane penetration depths of LiFeAs and LiFe(As,P) depend on temperature exponentially at low temperatures, which is a strong indication that these two materials have the nodeless superconducting gap. The temperature dependence of the superfluid density indicates that LiFeAs and LiFe(As,P) are multi-gap superconductors with at least two isotropic gaps. In FeSe sub(1-x)Te sub(x), on the other hand, the quadratic temperature dependence of the in-plane penetration depth appears, which indicates the existence of some sort of quasiparticle excitations. In addtion, the real part of the microwave conductivity exhibits a large enhancement below T sub(c) in all three materials, which results from the increase of the quasiparticle relaxation time, tau , below T sub(c).
ISSN:0921-4534
DOI:10.1016/j.physc.2011.05.013