Pressure 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>and charge transfer in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">YBa</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">Cu</mml:mi></mml:mrow><mml:mrow><mml:mn>3</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">O</mml:mi></mml:mrow><mml:mrow><mml:mi mathvariant="italic">x</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>(6.35≤<i>x</i>≤7) single crystals
Аннотация
The superconducting critical temperature ${\mathit{T}}_{\mathit{c}}$ of ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{\mathit{x}}$ single crystals (6.35\ensuremath{\lesssim}x\ensuremath{\lesssim}7) has been measured resistively as a function of pressure P (0\ensuremath{\le}P\ensuremath{\lesssim}20 kbar). The initial rate ${\mathit{dT}}_{\mathit{c}}$/dP exhibits three distinct regimes, a narrow plateau near x\ensuremath{\approxeq}7 with ${\mathit{dT}}_{\mathit{c}}$/dP\ensuremath{\approxeq}0.04 K/kbar, a plateau in the range 6.4\ensuremath{\lesssim}x\ensuremath{\lesssim}6.8, where ${\mathit{dT}}_{\mathit{c}}$/dP\ensuremath{\approxeq}0.43 K/kbar, and a maximum value \ensuremath{\sim}0.8 K/kbar at x\ensuremath{\approxeq}6.35. An analysis of the ${\mathit{T}}_{\mathit{c}}$(x,P) data using a phenomenological model yields a pronounced peak near x=6.8 in d\ensuremath{\Delta}${\mathit{n}}_{\mathit{h}}$(x)/dP, where \ensuremath{\Delta}${\mathit{n}}_{\mathit{h}}$(x) is the change in the hole density in the ${\mathrm{CuO}}_{2}$ planes relative to the value corresponding to the fully oxygenated sample.
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