Intercalated or substituted Cu atoms in Cu doped Bi2Se3 and Bi2Te3 topological insulators
Cheng-Maw Cheng1*, Wei-Chuan Chen1, Chia-Hung Chu1, Jih-Young Yuh1, Ku-Ding Tsuei1, Mitch Ming-Chi Chou2, Chao-Kuei Lee3,4, Hung-Duen Yang4
1National Synchrotron Radiation Research Center, Hsinchu, Taiwan
2Department of Materials and Optoelectronic Science, National Sun Yat-Sen University, Kaohsiung, Taiwan
3Department of Photonics, National Sun Yat-Sen University, Kaohsiung, Taiwan
4Department of Physics, National Sun Yat-Sen University, Kaohsiung, Taiwan
* presenting author:Cheng-Maw Cheng,
Topological insulator (TI) is a new class of quantum materials with attractive properties for physics and applications. The Cu-doped Bi2Se3 has been proposed as a candidate of topological superconductor with the transition temperature below 3 K. In contrast to Cu-doped Bi2Se3 compound, only few studies focused on Cu-doped Bi2Te3 topological insulator and the superconductivity in this system was not observed. To understand the origin of superconductivity in Bi2Se3 system, the sites of Cu atoms in these systems is a crucial problem. Bismuth family TIs (Bi2Se3, Bi2Te3 and Sb2Te3 ) have tetradymite structure, which consists of covalently bonded quintuple layers (QLs) and has weakly interaction of van der Waals force within QLs. The Cu atoms can be intercalated into the spacing of QLs or replace the Bi sites. To clarify this problem, here, we conduct angle-resolved photoemission spectroscopy (ARPES) experiment, X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) in Cu-dpoed Bi2Se3 and Bi2Te3 single crystals. A series of Cu-doped Bi2Se3 and Bi2Te3 with the various content of Cu atoms were grown by the floating zone method. Our results from ARPES, XAS and XRD suggest that most Cu atoms are intercalated into the van der Waals gap in Cu-doped Bi2Se3, but the situation of substituted Cu atoms is dominant in Bi2Te3 compounds.

Keywords: topological insulator, ARPES, XAS, Superconductivity