Unravelling the mechanism of the semiconducting-like behavior and its relation to superconductivity in (CaFe1−xPtxAs)10Pt3As8

Abstract

The temperature-dependence of the in-plane optical properties of (CaFe1−xPtxAs)10Pt3As8 have been investigated for the undoped (x=0) parent compound, and the optimally doped (x=0.1) superconducting material (Tc≃12 K) over a wide frequency range. The optical conductivity has been described using two free-carrier (Drude) components, in combination with oscillators to describe interband transitions. At room temperature, the parent compound may be described by a strong, broad Drude term, as well as a narrow, weaker Drude component. Below the structural and magnetic transitions at ≃96 and 83 K, respectively, strength is transferred from the free-carrier components into a bound excitation at ≃1000cm−1, and the material exhibits semiconducting-like behavior. In the optimally doped sample, at room temperature the optical properties are again described by narrow and broad Drude responses comparable to the parent compound; however, below T*≃100 K, strength from the narrow Drude is transferred into a newly emergent low-energy peak at ≃120cm−1, which arises from a localization process, resulting in semiconducting-like behavior. Interestingly, below Tc, this peak also contributes to the superfluid weight, indicating that some localized electrons condense into Cooper pairs; this observation may provide insight into the pairing mechanism in iron-based superconductors.

Source-reported materials — not catalogue approval

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