Doping Dependence of Upper Critical Field of High-Tc Cuprate Bi2+xSr2−xCaCu2O8+δ Estimated from Irreversibility Field at Zero Temperature

• Published in: Journal of the Physical Society of Japan 2024-10, Vol.93 (10), p.1
• Main Authors: Kato, Junichiro, Ishida, Shigeyuki, Okada, Tatsunori, Nakagawa, Shungo, Mino, Yutaro, Higashi, Yoichi, Kashiwagi, Takanari, Awaji, Satoshi, Iyo, Akira, Ogino, Hiraku, Mawatari, Yasunori, Takeshita, Nao, Yoshida, Yoshiyuki, Eisaki, Hiroshi, Nishio, Taichiro
• Format: Article
• Language: English
• Subjects: Bismuth strontium calcium copper oxide; Critical field (superconductivity); Doping; Hysteresis loops; Single crystals; Temperature dependence; YBCO superconductors
• ISSN: 0031-9015; 1347-4073
• DOI: 10.7566/JPSJ.93.104705

We investigated the temperature (T) dependence of the irreversibility field Hirr(T) in high-critical-temperature cuprate Bi2+xSr2−xCa1−yYyCu2O8+δ (Bi-2212) single crystals over a wide range of hole doping level (p). Hirr(T) was evaluated by measuring the magnetization hysteresis loop. The value of Hirr(T) extrapolated to T = 0 K [Hirr(0)], is either equal to or sets the lower boundary for the upper critical field at T = 0 K [Hc2(0)]. Tc shows a parabolic p-dependence (peak at p = 0.16), whereas μ0Hirr(0) increases monotonically with p by approximately one order of magnitude, from 19 T for the most underdoped sample (p = 0.065, Tc = 24 K) to 209 T for the most overdoped sample (p = 0.200, Tc = 75 K). The present results qualitatively agree with Hc2(0) values evaluated from the specific heat measurements. The observed p-dependence of Hirr(0) in Bi-2212 is distinct from those in YBa2Cu3O7−δ and HgBa2CuO6+δ, in which a pronounced dip structure appears in the underdoped region. Considering that the dip structures observed in these two systems are likely associated with the formation of competing orders (most likely field-induced charge orders), the present results indicate that the influence of the competing order in Bi-2212 is less prominent than that in the other two systems.