Metal-Insulator Transition in Ca-Doped Sr14-xCaxCu24O41 Systems Probed by Thermopower Measurements  

作　　者：王清波 徐象繁 陶前 王洪涛 许祝安 

机构地区：[1]Department of Physics, Zhejiang University, Hangzhou 310027 [2]Department of Physics and Information Science, Wenzhou University, Wenzhou 325027

出　　处：《Chinese Physics Letters》2008年第5期1857-1860,共4页中国物理快报（英文版）

基　　金：Supported by the National Basic Research Programme of China under Grant No 2007CB925001, and the Natural Science Foundation of Zhejiang Province under Grant No Y605106.

摘　　要：High quality Sr14-xCaxCu24O41 single-crystals are successfully grown by floating-zone technique, and the trans- port properties are studied. The temperature dependence of resistivity along the c-axis direction is semiconductor- like for x ≤ 10 and it can be fitted by the thermal activation equation p = po exp（ △ /kBT） with kB being the Boltzmann constant and A the activation energy. A break in the slope of thermopower （S） versus the inverse temperature （1 IT） corresponding to the formation of charge-density waves （CD W） is first observed for x ≤ 6. The temperature dependence of thermopower becomes metallic for x ≥ 8 while the resistivity is still semiconductorlike. We propose that the insulation behaviour of the resistivity in the Ca doping range 8 ≤ x ≤ 11 could result from the localization of the charge carriers due to the disorder induced by Ca doping and a revised electronic phase diagram is derived based on our observations.High quality Sr14-xCaxCu24O41 single-crystals are successfully grown by floating-zone technique, and the trans- port properties are studied. The temperature dependence of resistivity along the c-axis direction is semiconductor- like for x ≤ 10 and it can be fitted by the thermal activation equation p = po exp（ △ /kBT） with kB being the Boltzmann constant and A the activation energy. A break in the slope of thermopower （S） versus the inverse temperature （1 IT） corresponding to the formation of charge-density waves （CD W） is first observed for x ≤ 6. The temperature dependence of thermopower becomes metallic for x ≥ 8 while the resistivity is still semiconductorlike. We propose that the insulation behaviour of the resistivity in the Ca doping range 8 ≤ x ≤ 11 could result from the localization of the charge carriers due to the disorder induced by Ca doping and a revised electronic phase diagram is derived based on our observations.

关 键 词：TRANSPORT-PROPERTIES SINGLE-CRYSTALS SPIN GAP LADDERS SUPERCONDUCTIVITY SR14CU24O41 STATE A=BA 

分 类 号：O46[理学—电子物理学]