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Metal--Insulator Transition in Ca-Doped Sr14-xCaxCu24O41 Systems Probed by Thermopower Measurements |
| WANG Qing-Bo1;XU Xiang-Fan1;TAO Qian1;WANG Hong-Tao2;XU Zhu-An1 |
| 1Department of Physics, Zhejiang University, Hangzhou 3100272Department of Physics and Information Science, Wenzhou University, Wenzhou 325027 |
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| Cite this article: |
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WANG Qing-Bo, XU Xiang-Fan, TAO Qian et al 2008 Chin. Phys. Lett. 25 1857-1860 |
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Abstract High quality Sr14-xCaxCu24O41 single-crystals are successfully grown by floating-zone technique, and the transport 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 ρ=ρ0exp(Δ/kBT) with k_B being the Boltzmann constant and Δ the activation energy. A break in the slope of thermopower (S) versus the inverse
temperature (1/T) corresponding to the formation of charge-density waves (CDW) is first observed for x≤6. The temperature dependence of thermopower becomes metallic for x≥8 while the resistivity is still semiconductor-like. 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.
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| Keywords:
74.72.Jt
74.25.Fy
71.45.Lr
71.30.+h
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Received: 25 February 2008
Published: 29 April 2008
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