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arXiv 2011.03912cond-mat.supr-concond-mat.mes-hall
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在拓扑约瑟夫森结中观察分数约瑟夫森效应的最佳条件

Optimal Conditions for Observing Fractional Josephson Effect in Topological Josephson Junctions

Yeongmin Jang, Yong-Joo Doh

摘要:

拓扑约瑟夫森结(JJ)含有Majorana束缚态,在微波辐射下呈现4个$π$周期的电流-相位关系,从而产生双Shapiro台阶.我们进行了数值计算的拓扑JJ的动力学性质,使用一个修改的电容和电容并联结模型和广泛的研究作为结参数和微波功率和频率的函数的Shapiro步骤的逐步演变。我们的计算结果表明,奇整数夏皮罗步骤,即,分数交流约瑟夫森效应的证据,通过结电容和IcRn乘积的增加以及微波频率的降低而显著增强,即使对于4 $π$周期性超电流的相同部分。我们的研究提供了观察分数交流约瑟夫森效应的最佳条件,此外,我们的新模型可以用来精确地量化拓扑超导体的实验数据的拓扑超导电流。

英文摘要:

Topological Josephson junctions (JJs), which contain Majorana bound states, are expected to exhibit 4$π$-periodic current-phase relation, thereby resulting in doubled Shapiro steps under microwave irradiation. We performed numerical calculations of dynamical properties of topological JJs using a modified resistively and capacitively shunted junction model and extensively investigated the progressive evolution of Shapiro steps as a function of the junction parameters and microwave power and frequency. Our calculation results indicate that the suppression of odd-integer Shapiro steps, i.e., evidence of the fractional ac Josephson effect, is enhanced significantly by the increase in the junction capacitance and IcRn product as well as the decrease in the microwave frequency even for the same portion of the 4$π$-periodic supercurrent. Our study provides the optimal conditions for observing the fractional ac Josephson effect; furthermore, our new model can be used to precisely quantify the topological supercurrent from the experimental data of topological JJs.

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