arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2109.06285cond-mat.mes-hallcond-mat.supr-con
收藏

大磁场下NbN/graphene结中的Andreev反射

Andreev Reflections in NbN/graphene Junctions under Large Magnetic Fields

Da Wang, Evan J. Telford, Avishai Benyamini, John Jesudasan, Pratap Raychaudhuri, Kenji Watanabe, Takashi Taniguchi, James Hone, Cory R. Dean, Abhay N. Pasupathy

摘要:

混合超导体/石墨烯(SC/g)结是研究库珀对和量子霍尔(QH)边缘模之间相关性的极好候选材料。实验研究具有挑战性,因为Andreev反射对结无序极其敏感,并且需要高磁场来形成QH边缘状态。我们制作了低电阻SC/g界面,由石墨烯边缘与NbN接触组成,势垒强度为$Z\approx 0.4$,在大于$18$ T的磁场下保持超导。我们建立了零场Andreev反射的石墨烯的狄拉克能带结构的作用,并通过移动镜面反射和逆Andreev反射与平行磁场之间的边界来展示Andreev反射光谱的动态可调谐性。通过施加垂直磁场,我们观察到由于NbN/g界面Andreev过程效率降低,导致$ν= 4$ Landau能级2探针电导的振荡抑制,这与理论预测一致.

英文摘要:

Hybrid superconductor/graphene (SC/g) junctions are excellent candidates for investigating correlations between Cooper pairs and quantum Hall (QH) edge modes. Experimental studies are challenging as Andreev reflections are extremely sensitive to junction disorder and high magnetic fields are required to form QH edge states. We fabricated low-resistance SC/g interfaces, composed of graphene edge contacted with NbN with a barrier strength of $Z\approx 0.4$, that remain superconducting under magnetic fields larger than $18$ T. We establish the role of graphene's Dirac band structure on zero-field Andreev reflections and demonstrate dynamic tunability of the Andreev reflection spectrum by moving the boundary between specular and retro Andreev reflections with parallel magnetic fields. Through the application of perpendicular magnetic fields, we observe an oscillatory suppression of the 2-probe conductance in the $ν= 4$ Landau level attributed to the reduced efficiency of Andreev processes at the NbN/g interface, consistent with theoretical predictions.

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。

↑