Theoretical studies for the intrinsic Josephson effect and the collective excitations in high-Tc superconductors

高T_c铜酸盐中的CuO_2层是这些体系中高温超导电性的主要原因。高温超导体中CuO_2层间的耦合很弱。因此，即使在这些超导体的单晶中，也会在c轴输运现象中出现约瑟夫森效应，即本征约瑟夫森效应。在这个研究项目中，我从理论上研究了高T_c超导体中与本征约瑟夫森效应有关的c轴输运性质。我已经为在这些超导体中观察到的约瑟夫森等离子体振荡建立了一个完整的量子理论。该理论阐明了准粒子对等离子体激发的影响。本征约瑟夫森结阵列的c轴电荷动力学揭示了面内(ab面)面积减小时的尺寸依赖关系。这种现象是由库仑阻塞效应引起的。当面内面积减小到某一临界值WC以下时，系统中的等离子体振荡变得不稳定。在面内面积小于WC的系统中，c轴电荷动力学主要由单库珀对隧道效应所控制。我发展了一个重整化群理论来解释一系列本征约瑟夫森结中的库仑阻塞效应。推导出了WC值的显式表达式。

The CuO2 layers in high-Tc cuprates are responsible for the high-temperature superconductivity in these systems. The coupling between Cu02 layers in high-Tc superconductors is very weak. As a result, the Josephson effect appears in the c-axis transport phenomena even in single crystals of these superconductors, which is called the intrinsic Josephson effect. In this research project I have investigated theoretically the c-axis transport properties related to the intrinsic Josephson effects in high-Tc superconductors. I have constructed a complete quantum theory for the Josephson plasma oscillations observed in these superconductors. The effects of the quasi-particles on the plasma excitations were clarified in this theory. The c-axis charge dynamics in an array of the intrinsic Josephson junctions reveals the size dependence when the in-plane (ab-plane) area is decreased. This phenomena is caused by the Coulomb blockade effect. The plasma oscillations in this system become unstable when the in-plane area decreases below some critical value, Wc. The c-axis charge dynamics in the system with an in-plane area less than Wc is dominated by the single Cooper-pair tunneling. I have developed a renormalization group theory for the Coulomb blockade effect in an array of the intrinsic Josephson junctions. The explicit expression for Wc was derived.