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arXiv 2103.16113cond-mat.supr-concond-mat.mes-hall
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4π周期约瑟夫森电流作用下Shapiro台阶的特征

Characterization of Shapiro steps in the presence of a 4π-periodic Josephson current

Jinho Park, Yong-Bin Choi, Gil-Ho Lee, Hu-Jong Lee

摘要:

位于拓扑超导体边界的马约拉纳零能模(Majorana zero-energy modes,MZMs)最近引起了人们极大的兴趣,因为它们提供了一个探索基础物理如非阿贝尔统计和容错量子计算的平台。微波辐照下约瑟夫森结中Shapiro台阶的倍周期被认为是结边缘MZM出现的有力证据。然而,问题仍然是如何的夏皮罗步骤响应的存在下,一个4π周期约瑟夫森电流。本文研究了Shapiro台阶与4π周期电流与拓扑平凡的2π周期电流之比(α)、结的约化微波频率(Ω)和McCumber参数(β)的关系。我们的分析再现了与针对α、Ω({ \lesssim 0.1})和β({gtrsim 1.0})的特定参数集实验观察到的那些类似的Shapiro步骤。完全抑制n=1阶跃的第一波瓣保证了4π周期约瑟夫森电流的存在.此外,我们还讨论了即使在小α({<0.1})情况下,完全抑制{n=1}阶跃的第一波瓣所需的Ω和β的范围.为了观察“倍周期Shapiro台阶”,即使α很小,结也应该有大的{I_c}{R_N}积和足够大的结电容。

英文摘要:

The Majorana zero-energy modes (MZMs) residing at the boundary of topological superconductors have attracted a great deal of interest recently, as they provide a platform to explore fundamental physics such as non-Abelian statistics, as well as fault-tolerant quantum computation. Period doubling of Shapiro steps in a Josephson junction under microwave irradiation has been regarded as strong evidence for the emergence of the MZMs at the junction edges. However, questions remain as to how the Shapiro steps respond to the presence of a 4π-periodic Josephson current. In this study, we investigated the characteristic features of Shapiro steps with respect to the ratio (α) of the 4π-periodic current to the topologically trivial 2π-periodic one, as well as the reduced microwave frequency (Ω) and McCumber parameter (β) of the junction. Our analysis reproduced Shapiro steps similar to those observed experimentally for specific parameter sets of α,Ω ({\lesssim 0.1}), and β ({gtrsim 1.0}). Full suppression of the first lobe of the n=1 step guarantees the presence of a 4π-periodic Josephson current.In addition, we discuss the range of Ω and β needed for full suppression of the first lobe of the {n=1} step, even for small α ({<0.1}). To observe "period-doubled Shapiro steps", even with a small α, the junction should have a large {I_c}{R_N} product and sufficiently large junction capacitance.

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。

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