Unprecedented high irreversibility line in the nontoxic cuprate superconductor (Cu,C)Ba<sub>2</sub>Ca<sub>3</sub>Cu<sub>4</sub>O<sub>11+δ</sub>.

Zhang, Yue; Liu, Wenhao; Zhu, Xiyu; Zhao, Haonan; Hu, Zheng; He, Chengping; Wen, Hai-Hu · Sci Adv · 2018

basic_science · Level V

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Abstract

One of the key factors that limit the high-power applications for a type II superconductor is the irreversibility line <i>H</i> <sub>irr</sub>(<i>T</i>), which reflects the very boundary of resistive dissipation in the phase diagram of magnetic field versus temperature. In cuprate family, the Y-, Bi-, Hg-, and Tl-based systems have superconducting transition temperatures exceeding the liquid nitrogen boiling temperature (~77 K). However, the toxic elements Hg and Tl in the latter two systems strongly constrain the applications. The best perspective so far is relying on the YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-δ</sub> (<i>T</i> <sub>c</sub> ≈ 90 K) system, which is nontoxic and has a relatively high irreversibility magnetic field. We report the study of a nontoxic superconductor (Cu,C)Ba<sub>2</sub>Ca<sub>3</sub>Cu<sub>4</sub>O<sub>11+δ</sub> with <i>T</i> <sub>c</sub> = 116 K. We found that the irreversibility magnetic field is extremely high, and it thus provides great potential for applications above the liquid nitrogen temperature.