We theoretically reveal the unusual features of the Josephson effect in a strained zigzag graphene nanoribbon with a small length relative to the superconducting coherence length and an arbitrary width. We find a step-wise variation of the critical supercurrent with the width of the nanoribbon, showing additional small width plateaus placed between the wide steps of a non-strained structure. We further demonstrate the peculiar quantization of the critical supercurrent in terms of the strain, resulted from the coupling of the pseudospin of Dirac fermions with the strain-induced gauge potential, where the height of the steps decreases with growing the strength of the fictitious gauge potential. Moreover, our results determine the potential of the proposed superconducting quantum point contact for the realization of the supercurrent switch under an applied strain. Besides, we find that the local density of states of the strained zigzag nanoribbon displays a crossover between the decaying and oscillating behavior with the distance from the edges, by tuning the width and Fermi wavelength of the nanoribbon.

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与应变石墨烯纳米带量子点接触的新超电流模式

我们从理论上揭示了应变之字形石墨烯纳米带中约瑟夫森效应的不寻常特征，该纳米带相对于超导相干长度和任意宽度具有较小的长度。我们发现临界超电流随纳米带宽度的逐步变化，显示出放置在非应变结构的宽台阶之间的额外小宽度平台。我们进一步证明了临界超电流在应变方面的特殊量化，这是由狄拉克费米子的赝自旋与应变诱导的规范电位耦合引起的，其中台阶的高度随着虚拟规范电位强度的增加而减小. 而且，我们的结果确定了所提出的超导量子点接触在施加应变下实现超电流开关的潜力。此外，我们发现通过调整纳米带的宽度和费米波长，应变之字形纳米带的局部状态密度在衰减和振荡行为与边缘距离之间显示出交叉。