Optical properties in the hole-doped Ca8.5Na1.5(Pt3As8)(Fe2As2)5 single crystal

W.J Choi,Y.I Seo,Shin-Ichi Kimura,Yong Seung Kwon

doi:10.1016/j.rinp.2021.104468

Abstract

For newly synthesized hole-doped Ca8.5Na1.5(Pt3As8)(Fe2As2)5 single crystals, we measured the infrared reflectivity spectrum and the magnetic field dependence of magnetoresistivity and Hall resistivity. The results of these two experiments in normal states are well described by two band models. In normal states below 150 K, the optical conductivity spectrum shows the transfer of spectral weights from the mid-infrared region to the near-infrared region by Hund's coupling, a strong correlation effect. Meanwhile, the carrier concentration evaluated by magnetoresistivity and Hall resistivity decreases significantly at 150 K due to the formation of pseudogap. In the superconducting state, the spectral weight in the low frequency region by the superconducting condensate is completely suppressed, which is well analyzed by the generalized Mattis-Bardeen (M-B) model with a two superconducting gap.

Highlights

The recently discovered superconducting Ca10(Pt3As8)(Fe2As2)[5] has been added to another new family of iron-based superconductors[1,2,3]
The sum of the carrier concentrations for the two normal component bands in the superconducting state is similar to that of the broad Drude band in the normal state, because the magnitude of (ΩPsn1)2 + (ΩPsn2)[2] is almost same as that of (ΩP1)[2]. These results indicate that the two types of superconducting gaps obtained by fitting above are derived from the same broad Drude band obtained in the normal state, which may physically mean that an anisotropic superconducting gap with nodes was formed in the broad Drude band
Optical conductivity is well-fitted by the L-D model with two Drude responses and eight Lorentzian oscillators, and conductivity tensors σxx(B) and σxy(B) are well-fitted using a two-band model

Summary

Introduction

The recently discovered superconducting Ca10(Pt3As8)(Fe2As2)[5] ( called Ca10-3-8) has been added to another new family of iron-based superconductors[1,2,3] This superconductor exhibits the behavior of a prototype between the subtle competition and coexistence of magnetism and superconductivity found in other iron-based superconductors. This compound shows a stacked crystal structure of a Ca-(Pt3As8)-Ca-(Fe2As2) layer, where the Ca layer serves as a reservoir layer that supplies electric charges to the Fe2As2 layer, and the Pt3As8 layer serves as an intermediate layer controlling the distance between the Fe2As2 layers[1]. Our material is one of the few candidates to study Tc enhancement in iron-based superconductors, and has attracted much attention in the field of superconductivity

Methods

Results

Conclusion