Fermi Velocity Dependent Critical Current in Ballistic Bilayer Graphene Josephson Junctions

IF 4.8 Q2 NANOSCIENCE & NANOTECHNOLOGY

ACS Nanoscience Au Pub Date : 2025-03-19 DOI:10.1021/acsnanoscienceau.4c0008010.1021/acsnanoscienceau.4c00080

Amis Sharma, Chun-Chia Chen, Jordan McCourt, Mingi Kim, Kenji Watanabe, Takashi Taniguchi, Leonid Rokhinson, Gleb Finkelstein and Ivan Borzenets*,

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Abstract

We perform transport measurements on proximitized, ballistic, bilayer graphene Josephson junctions (BGJJs) in the intermediate-to-long junction regime (L > ξ). We measure the device’s differential resistance as a function of bias current and gate voltage for a range of different temperatures. The extracted critical current I_C follows an exponential trend with temperature: exp(−k_BT/δE). Here δE = ℏν_F/2πL: an expected trend for intermediate-to-long junctions. From δE, we determine the Fermi velocity of the bilayer graphene, which is found to increase with gate voltage. Simultaneously, we show the carrier density dependence of δE, which is attributed to the quadratic dispersion of bilayer graphene. This is in contrast to single layer graphene Josephson junctions, where δE and the Fermi velocity are independent of the carrier density. The carrier density dependence in BGJJs allows for additional tuning parameters in graphene-based Josephson junction devices.

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弹道双层石墨烯约瑟夫森结中依赖费米速度的临界电流

我们在中长结态（L > ξ）下对近似、弹道、双层石墨烯约瑟夫森结（BGJJs）进行了传输测量。我们测量了该器件在不同温度范围内的差分电阻与偏置电流和栅极电压的函数关系。提取的临界电流 IC 随温度呈指数趋势：exp(-kBT/δE)。这里 δE = ℏνF/2πL：这是中长结的预期趋势。根据δE，我们确定了双层石墨烯的费米速度，发现它随着栅极电压的增加而增加。同时，我们还显示了 δE 的载流子密度依赖性，这归因于双层石墨烯的二次色散。这与单层石墨烯约瑟夫森结形成鲜明对比，在单层石墨烯约瑟夫森结中，δE 和费米速度与载流子密度无关。双层石墨烯约瑟夫森结中的载流子密度依赖性为基于石墨烯的约瑟夫森结器件提供了额外的调整参数。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

ACS Nanoscience Au 材料科学、纳米科学-

CiteScore

4.20

自引率

0.00%

发文量

期刊介绍： ACS Nanoscience Au is an open access journal that publishes original fundamental and applied research on nanoscience and nanotechnology research at the interfaces of chemistry biology medicine materials science physics and engineering.The journal publishes short letters comprehensive articles reviews and perspectives on all aspects of nanoscience and nanotechnology:synthesis assembly characterization theory modeling and simulation of nanostructures nanomaterials and nanoscale devicesdesign fabrication and applications of organic inorganic polymer hybrid and biological nanostructuresexperimental and theoretical studies of nanoscale chemical physical and biological phenomenamethods and tools for nanoscience and nanotechnologyself- and directed-assemblyzero- one- and two-dimensional materialsnanostructures and nano-engineered devices with advanced performancenanobiotechnologynanomedicine and nanotoxicologyACS Nanoscience Au also publishes original experimental and theoretical research of an applied nature that integrates knowledge in the areas of materials engineering physics bioscience and chemistry into important applications of nanomaterials.