低维氧化物输运特性研究

In low dimensional oxides, such as high-Tc superconducting cuprates, various physical phenomena have been revealed due to the low dimensional structure and strong electron correlation. The experimental probes such as resistivity, Hall effect, and thermo-electric power are employed to study the transport properties versus doping level, temperature, and magnetic field, in order to understand the electronic phase diagram, low energy excitations and the underlying interactions. The main results are summarized as below: (1) A empiristic formula for the relation between the room temperature thermo-electric power and carrier concentration in La2-xSrxCuO4 system was proposed by studying its thermo-electric power and the vortex-like excitation above Tc was found to be strictly in-plane by measuring the Nernst effect; (2) The characteristics temperatures related to the pseudogap defined by the temperature dependence of Hall effect, a novel magnetic field dependence of Hall conductivity in mixed state, and vortex-like excitations above Tc in pseudogap region was established in oxygen-depleted, Zn and Co doped Ya-Ba-Cu-O by studying the transport properties; (3) The ferromagnetic order in the superconductor EuSr2RuCu2O8 was studied; (4) The ground state of a vortex system with random pinning was studied by the dynamic approach and the simulated result on the vortex structure versus the magnetic flux density is consistent with the experimental findings; (5) The thermal stability and high temperature dependence of the resistivity for the recently discovered superconductor MgB2 was studied and the Debye temperature was deduced to be about 1200℃. (6) The crystals of two types of charge-density wave (CDW) materials, K0.33MoO3、K0.3MoO3 and NbSe3 were prepared successfully and a novel asymmetric modulation of the transverse current effect was found in K0.3MoO3 by measuring the I-V characteristics.

目前在理论上和实验上还没有成功的方法来处理低维铜氧、锰氧化合物电子间的强库仑相互作用与元激发行为。本项目拟通过低掺杂的铜氧化物如YBCO、镍氧系化合物如Y2BaNiO5、萄跸祷衔锶鏟rCaMnO等低维氧化物的低温输运性质系统的实验和理论研究来揭示其中的准粒子行为，从而为建立在此类新型元激发基础上的电子器件开发指明方向，并为最终解决高Tc理论问题作出贡献。........