Unusual hole dependence of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="italic">T</mml:mi></mml:mrow><mml:mrow><mml:mi mathvariant="italic">c</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>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">CuO</mml:mi></mml:mrow><mml:mrow><mml:mn>4</mml:mn><mml:mo>+</mml:mo><mml:mi mathvariant="normal">δ</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>

The anion doping effect on the superconducting transition temperature (${\mathit{T}}_{\mathit{c}}$) of ${\mathrm{HgBa}}_{2}$${\mathrm{CuO}}_{4+\mathrm{\ensuremath{\delta}}}$ has been determined with a wide ${\mathit{T}}_{\mathit{c}}$ variation. We found a parabolic variation of ${\mathit{T}}_{\mathit{c}}$ with \ensuremath{\delta} over the entire range of superconductivity. Remarkably, the dependence of ${\mathit{T}}_{\mathit{c}}$ on p (the number of holes per ${\mathrm{CuO}}_{2}$) has richer features: for \ensuremath{\delta}\ensuremath{\le}0.28, ${\mathit{T}}_{\mathit{c}}$ is parabolic in p, but with an unusual prefactor and p=0.72\ensuremath{\delta}, giving significantly less than two holes per oxygen; and for \ensuremath{\delta}&gt;0.28, a drastic departure from the parabolic ${\mathit{T}}_{\mathit{c}}$(p) occurs. Implications for the occurrence of superconductivity in this material are discussed.

Перевод пока недоступен