Ultra-high critical current densities of superconducting YBa2Cu3O7-δ thin films in the overdoped state

Abstract The functional properties of cuprates are strongly determined by the doping state and carrier density. We present an oxygen doping study of YBa 2 Cu 3 O 7-δ (YBCO) thin films from underdoped to overdoped state, correlating the measured charge carrier density, $${n}_{\mathrm{H}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>n</mml:mi> <mml:mi>H</mml:mi> </mml:msub> </mml:math> , the hole doping, p , and the critical current density, $${J}_{c}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>J</mml:mi> <mml:mi>c</mml:mi> </mml:msub> </mml:math> . Our results show experimental demonstration of strong increase of $${J}_{c}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>J</mml:mi> <mml:mi>c</mml:mi> </mml:msub> </mml:math> with $${n}_{\mathrm{H}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>n</mml:mi> <mml:mi>H</mml:mi> </mml:msub> </mml:math> , up to Quantum Critical Point (QCP), due to an increase of the superconducting condensation energy. The ultra-high $${J}_{c}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>J</mml:mi> <mml:mi>c</mml:mi> </mml:msub> </mml:math> achieved, 90 MA cm −2 at 5 K corresponds to about a fifth of the depairing current, i.e. a value among the highest ever reported in YBCO films. The overdoped regime is confirmed by a sudden increase of $${n}_{\mathrm{H}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>n</mml:mi> <mml:mi>H</mml:mi> </mml:msub> </mml:math> , associated to the reconstruction of the Fermi-surface at the QCP. Overdoping YBCO opens a promising route to extend the current carrying capabilities of rare-earth barium copper oxide (REBCO) coated conductors for applications.

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