Superconductivity up to 164 K in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">HgBa</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Ca</mml:mi></mml:mrow><mml:mrow><mml:mi mathvariant="italic">m</mml:mi><mml:mi mathvariant="normal">−</mml:mi><mml:mn>1</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Cu</mml:mi></mml:mrow><mml:mrow><mml:mi mathvariant="italic">m</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">O</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn><mml:mi mathvariant="italic">m</mml:mi><mml:mo>+</mml:mo><mml:mn>2</mml:mn><mml:mo>+</mml:mo><mml:mi mathvariant="normal">δ</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>(<i>m</i>=1, 2, and 3) under quasihydrostatic pressures
Abstract
The superconducting transition temperatures (${\mathit{T}}_{\mathit{c}}$'s) of optimally doped ${\mathrm{HgBa}}_{2}$${\mathrm{Ca}}_{\mathit{m}\mathrm{\ensuremath{-}}1}$${\mathrm{Cu}}_{\mathit{m}}$${\mathrm{O}}_{2\mathit{m}+2+\mathrm{\ensuremath{\delta}}}$ (Hg 1:2:m-1:m) with m=1, 2, and 3 and ${\mathrm{Hg}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Pb}}_{\mathit{x}}$${\mathrm{Ba}}_{2}$${\mathrm{Ca}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{8+\mathrm{\ensuremath{\delta}}}$ [Hg(xPb) 1:2:2:3] have been investigated resistively under quasihydrostatic pressures up to 45 GPa. There seems to be a universal upward shift of ${\mathit{T}}_{\mathit{c}}$ under pressure, regardless of m, for all Hg 1:2:m-1:m, implying a common origin for all compounds. Record high ${\mathit{T}}_{\mathit{c}}$'s of 164, 154, and 118 K were reached for the optimally doped Hg 1:2:m-1:m with m=3, 2, and 1, respectively. However, the ${\mathit{T}}_{\mathit{c}}$ enhancement is suppressed by Pb substitution, suggesting the possibility that Hg plays an important role in these compounds.
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