聚焦离子束剪裁高$T_c$超导微结构中的零交叉Shapiro台阶
Zero-crossing Shapiro steps in focused-ion-beam-tailored high-$T_c$ superconducting microstructures
摘要：
研究了S形Bi $_2$ Sr $_2$ CaCu_2 O $_{8+x}$（Bi-2212）微米尺度样品的微波响应特性。用聚焦离子束的治疗使我们能够降低等离子体频率下降到$f_p$ $\sim$ 5 GHz，在$T$ =0.3 K的自然堆叠的约瑟夫森结中的晶体。我们在低至$\sim$ 5 GHz的频率下观察到Shapiro台阶。在低至$\sim$ 10 GHz的频率下观察到了良好的零交叉Shapiro台阶。它们表现为恒压平台，在零偏置电流下出现非零电压。我们证实了当辐照频率足够大于$f_p$时，可以在Bi-2212堆叠结中观察到零交叉Shapiro台阶。观察到的高阶分数阶微波响应表明，层间耦合的Bi-2212约瑟夫森结具有非正弦电流相位关系。基于台阶的温度依赖性，我们还表明，台阶的有限斜率是由于相扩散效应的增强。
英文摘要：
Microwave response of S-shaped Bi$_2$Sr$_2$CaCu2O$_{8+x}$ (Bi-2212) micron-scale samples, in which the supercurrent was forced to flow perpendicular to the crystal layers, was investigated. A treatment with a focused ion beam allowed us to reduce the plasma frequency down to $f_p$$\sim$5 GHz at $T$=0.3 K in naturally stacked Josephson junctions in a crystal. We observed Shapiro steps at frequencies as low as $\sim$5 GHz. Well-developed zero-crossing Shapiro steps were observed at frequencies as low as $\sim$10 GHz. They appeared as constant-voltage plateaus with a non-zero voltage occurring at zero bias current. We confirmed that zero-crossing Shapiro steps in the Bi-2212 stacked junctions can be observed when the irradiated frequency is sufficiently larger than $f_p$. The observed high-order fractional steps in the microwave responses indicate that the interlayer-coupled Bi-2212 Josephson junctions have nonsinusoidal current-phase relation. Based on the temperature dependence of the steps we also showed that the finite slope of the steps is due to the enhancement of the phase diffusion effect.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
