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Microwave electrodynamics of the high-Tc superconductor Tl2Ba2CuO6+delta Aghigh, Seyed Mahyad


The microwave surface resistance, Rs(w,T), and the magnetic penetration depth, ⋋(T), of a rectangular Tl₂Ba₂CuO₆+δ (Tl-2201) single crystal measured along its different crystallographic axes are reported. The measurements of the surface resistance as a function of frequency were made using a precise broadband bolometric technique, and a loop-gap resonator was employed to measure the temperature dependence of the magnetic penetration depth. Disentangling the in- and out-of-plane components of both microwave properties was accomplished by comparing the measurement results obtained for different orientations of the sample with respect to the applied magnetic field, allowing us to report, for the first time, the c-axis components of ∆⋋(T), and Rs(w,T). In particular, our results show a quadratic temperature dependence of ∆⋋c(T) in Tl-2201 which is similar to that in other anisotropic cuprates such as BSCCO, and YBCO. Furthermore, in the case of the surface resistance, a sign change in the curvature of Rc s(w) is observed. The origin of this behavior is not yet understood. The ab-plane components of both microwave properties behave similarly to those reported on other dopings of this material. The measurements of Rs(w,T) and ∆⋋(T) allow us to determine the complex conductivity of this material. Having Tc of 43 K, the sample studied here is in the middle of the overdoped side of the superconducting dome, where very few studies have been made. This particular sample possesses relatively low quasiparticle scattering rates making the interpretation of the measurement results more straightforward. The reliability of the results, current limitations, and further potential progress are also discussed.

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