A Reproducible Approach of Preparing High-Quality Overdoped Bi ₂ Sr ₂ CaCu ₂ O _{8+ δ} Single Crystals by Oxygen Annealing and Quenching Method

Abstract

We report a reproducible approach in preparing high-quality overdoped Bi2Sr2 CaCu2 O8+δ (Bi2212) single crystals by annealing Bi2212 crystals in high oxygen pressure followed by a fast quenching. In this way, high-quality overdoped and heavily overdoped Bi2212 single crystals are obtained by controlling the annealing oxygen pressure. We find that, beyond a limit of oxygen pressure that can achieve most heavily overdoped Bi2212 with a Tc ∼63 K, the annealed Bi2212 begins to decompose. This accounts for the existence of the hole-doping limit and thus the Tc limit in the heavily overdoped region of Bi2212 by the oxygen annealing process. These results provide a reliable way in preparing high-quality overdoped and heavily overdoped Bi2212 crystals that are important for studies of the physical properties, electronic structure and superconductivity mechanism of the cuprate superconductors.

Shockwave-Loading-Induced Enhancement of T c in Superconducting Bi2Sr2CaCu2O8+δ

“…It consists of three main phases: Bi 2 Sr 2 CuO 6 (Bi2201), Bi 2 Sr 2 CaCu 2 O 8 (Bi2212) and Bi 2 Sr 2 Ca 2 Cu 3 O 10 (Bi2223) 1–3 . Since their discovery in 1986, these cuprates have been viewed as exotic materials 4 and have been well-studied by surface-sensitive measurements such as angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy/spectroscopy (STM/STS) 5–9 . Among known superconductors in the large family of 2-D layered materials, Bi2212 exhibits a high superconducting transition temperature ( T c ).…”

Distinct Superconducting Gap on Two Bilayer-Split Fermi Surface Sheets in Bi2Sr2CaCu2O8+δ Superconductor*

“…The Fermi level is referenced by measuring on clean polycrystalline gold that is electrically connected to the sample or referenced to the nodal direction of Bi2212 superconductors where the superconducting gap is known to be zero. The overdoped Bi2212 single crystals with a T c at 75 K were obtained by annealing the as-grown Bi2212 sample under high oxygen pressure [25]. The samples were cleaved in situ at low temperature of 20 K and measured in ultrahigh vacuum with a base pressure better than 3×10 −11 mbar.…”