电-声机制致高温超导特性随掺杂量演变

Electron-Phonon Coupling Leading to High-Temperature Superconductivity with Doping Content Evolution

利用极性晶体中慢电子的运动规律提出基于BCS机理的分析模型.分析发现,掺杂导致铜氧化物的费米面电子分为低能费米电子和高能电子,并产生快电子效应.欠掺杂区高能电子与晶格振动发生作用形成赝隙,费米电子与晶格作用形成超导隙.赝隙和超导隙的竞争平衡导致欠掺杂区超导隙2Δ0和κBTc比值与高能费米电子速度v*F成正比,与费米速度vF成反比.掺杂量(x)与高能费米速度(v*F)相图是解释高温超导相图的基础.利用模型和(x-v*F)相图能够对欠掺杂区赝隙温度、能隙与κBTc比例随掺杂量增加而线性下降的现象给出简单解释,即最佳掺杂区2Δ0和κBTc比值为7.6、过掺杂区为4.3的常数.显示系统随掺杂量增加由"非传统"行为向接近传统行为再到金属行为演变的规律.

An analytical model is presented by using the motion law of slow electrons in the polar crystal and the BCS theory.It is discovered that,the electrons in Fermi surface dividing into lowenergy and high-energy electrons and leading to fast electron effects in doping copper oxides.The pseudogap arises from the interactions between the high-energy electrons and phonon,the energy gap from those between Fermi electrons and phonon.The competitiveness between pseudogapΔp and energy gapΔ0lead to theΔ0-to-Tcratio proportional to high-energy velocity VF^＊and inverse to Fermi velocity VF.The high-temperature superconductivity with the doping evolution is explained based on the phase diagram（x-VF^＊）of the high-energy velocity varying with doping levels.By the model and the phase diagram,it can simply explain that the pseudogap temperature and theΔ0-to-Tcratio falls linearly with doping added in the under doping ranges,theΔ0-to-Tcratio being 7.6in the optimal doping ranges,4.3in the over doping ranges.It indicates that the superconductivity in cuprates evolving from ＂nonconventional＂to nearly conventional,and eventually to BCS behavior with doping added.