【摘要】 在CuO₂平面以外的阳离子格点通过改变Gd含量引入了无序.研究了Nd_1.85-xGd_xCe_0.15CuO₄单晶的电阻率ρ、霍耳系数R_H和热电势S.霍耳系数R_H的测量证明这种名义掺杂的改变并没有明显改变载流子的密度.热电势S（T）在120 K以上可用一个掺杂的半经验模型来分析,结果表明存在电子的窄能带和宽能带的共存.无论是电子态密度的带宽和有效电导率的带宽都随着x增加,而局域化的趋势随Gd掺杂增加明显增强.Gd掺杂对超导转变温度T_C的抑制作用很显著.在二维剩余电阻率ρ02D增加超过临界值h/4e²时没有发生超导-绝缘体转变,观察到的却是超导和局域化的共存效应.量子干涉效应不可以定性地解释Gd掺杂对于电子型超导体的超导转变温度T_c的抑制.更多还原

【Abstract】 Doping Gd into the cation sites outside the CuO₂ planes introduce the disorder.The resistivity p（T）,Hall coefficient R_H,and thermopower S（T）are studied for Nd_1.85-x Gd_xCe_0.15CuO₄ single crystals.It is confirmed by R_H measurement,such doping nominally does not change the carrier density.The S（T）data above 120 K is analyzed in terms of a semiempirical model.The results support the coexistence of a broad band and a narrow electron band.Both the bandwidths of the effective conductivity and the density of states and the tendency for localization increase with increasing Gd doping content x.The doping strongly depressed the superconducting transition temperature T_c.When the two dimensional residual resistivity ρ_02D increase more than the critical value h/4e²,the superconducting-insulator transition does not occur,while the co-existence of superconductivity and localization effect is observed.The quantum interference effect can not qualitatively interpret the depress of the superconducting transition temperature T_c.更多还原