Lin Shi-Zeng, Hu Xiao
WPI Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba 305-0044, Japan.
J Nanosci Nanotechnol. 2011 Apr;11(4):2916-21. doi: 10.1166/jnn.2011.3907.
The nano-scale intrinsic Josephson junctions in highly anisotropic cuprate superconductors have potential for generation of terahertz electromagnetic waves. When the thickness of a superconductor sample is much smaller than the wavelength of electromagnetic waves in vacuum, the superconductor renders itself as a cavity. Unlike conventional lasers, the presence of the cavity does not guarantee a coherent emission because of the internal degree of freedom of the superconductivity phase in long junctions. We study the excitation of terahertz wave by solitons in a stack of intrinsic Josephson junctions, especially for relatively short junctions. Coherent emission requires a rectangular configuration of solitons. However such a configuration is unstable against weak fluctuations, contrarily solitons favor a triangular lattice corresponding to an out-phase oscillation of electromagnetic waves. To utilize the cavity, we propose to use an array of stacks of short intrinsic Josephson junctions to generate powerful terahertz electromagnetic waves. The cavity synchronizes the plasma oscillation in different stacks and the emission intensity is predicted to be proportional to the number of stacks squared.
高度各向异性的铜酸盐超导体中的纳米级本征约瑟夫森结具有产生太赫兹电磁波的潜力。当超导体样品的厚度远小于真空中电磁波的波长时，超导体就会成为一个腔体。与传统激光器不同，由于长结中超导相位的内部自由度，腔体的存在并不能保证产生相干发射。我们研究了本征约瑟夫森结堆叠中孤子对太赫兹波的激发，特别是对于相对较短的结。相干发射需要孤子呈矩形排列。然而，这种排列对微弱波动不稳定，相反，孤子倾向于对应电磁波异相振荡的三角晶格。为了利用该腔体，我们建议使用短本征约瑟夫森结堆叠阵列来产生强大的太赫兹电磁波。该腔体使不同堆叠中的等离子体振荡同步，预计发射强度与堆叠数的平方成正比。
