Eur. Phys. J. B (2012) 85: 414
https://doi.org/10.1140/epjb/e2012-30975-2

Regular Article

Suppression of superconductivity in layered Bi₄O₄S₃ by Ag doping

¹ Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, P.R. China
² High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei 230031, P.R. China

^a e-mail: ypsun@issp.ac.cn

Received: 3 September 2012
Published online: 24 December 2012

Abstract

We report X-ray diffraction, magnetization and transport measurements for polycrystalline samples of the new layered superconductor Bi_4−xAg_xO₄S₃ (0 ≤ x ≤ 0.2). The superconducting transition temperature (T_C) decreases gradually and finally suppressed when x < 0.10. Accordingly, the resistivity changes from a metallic behavior for x < 0.1 to a semiconductor-like behavior for x > 0.1. The analysis of Seebeck coefficient shows there are two types of electron-like carriers dominate at different temperature regions, indicative of a multiband effect responsible for the transport properties. The suppression of superconductivity and the increased resistivity can be attributed to a shift of the Fermi level to the lower-energy side upon doping, which reduces the density of states at E_F. Further, our result indicates the superconductivity in Bi₄O₄S₃ is intrinsic and the dopant Ag prefers to enter the BiS₂ layers, which may essentially modify the electronic structure.