Pressure induced Superconductivity in the Copper Intercalated Bi₂Te_2.7Se_0.3 Single Crystal

Fan Yun Chiu^1*, Min Nan Ou (歐敏男)¹, Tsu Lien Hung (洪慈蓮)¹, Zih Gin Yu (余日靖)¹, Cheng Lung Chen (陳正龍)¹, Yang Yuan Chen (陳洋元)¹

¹Institute of Physics, Academia Sinica, Taipei, Taiwan

* Presenter:Fan Yun Chiu, email:fychiu@gate.sinica.edu.tw

The superconductivity at high pressures of copper intercalated Bi₂Te_2.7Se_0.3 single crystals is well studied in this work. Based on the well-known topological insulator Bi₂Te₃, the n-type Bi₂Te_2.7Se_0.3 single crystals are synthesized by means of the Bridgman method. Results of powder x-ray diffraction confirmed the rhombohedral structure of the Bi₂Te_2.7Se_0.3. The followed up thermal diffusing technique was employed to insert the copper into the weak van der Waal gap to form the Cu_xBi₂Te_2.7Se_0.3 crystal. The existence of copper is confirmed by using an electron probe micro analyzer (EPMA), which implies that the amount of copper x is about 0.04. A peered small crystal with dimensions of 100 μm × 100 μm × 15 μm in width, length, and thickness, respectively, is load into a diamond anvil cell for in-situ temperature and magnetic field dependent electrical resistance and Hall effect measurements at various pressures up to 10 GPa. As pressure increases, the superconducting transition temperature is obviously increased to ~4 K at 6.8 GPa. Meanwhile, the suppression of superconductivity by applying magnetic fields identified the characteristic of superconductivity. The investigation of anisotropic superconductivity is realized via resistance measurements at various magnetic fields, while the critical field H_c2 = 0.6 Tesla Tesla on B∥ab-plane is obviously higher than that of on B⊥ab-plane. Furthermore, the dramatically increasing of carrier concentration at the pressure nearby 6.58 GPa implying that the pop up of superconductivity is strongly related to the electrical band structure modification by pressure.

Keywords: pressure induced, Cu_xBi₂Te_2.7Se_0.3, superconductivity