Highly tunable junctions and non-local Josephson effect in magic-angle graphene tunnelling devices
Highly tunable junctions and non-local Josephson effect in magic-angle graphene tunnelling devices
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DOI：
10.1038/s41565-021-00894-4
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发表时间：
2021-05-03
影响因子：
38.3
通讯作者：
Jarillo-Herrero, Pablo
中科院分区：
文献类型：
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作者：
Rodan-Legrain, Daniel;Cao, Yuan;Jarillo-Herrero, Pablo
魔角扭曲双层石墨烯具有多种相，如金属态、绝缘体态和超导体态。现在，由这种二维材料平台制成的局部静电门控器件可以实现高度可调谐的约瑟夫森结，边缘隧道光谱和单电子晶体管操作。魔角扭曲双层石墨烯（MATBG）是一种高度可调的二维材料平台，具有多种相，如金属态、绝缘体态和超导体态。对这些相的局部静电控制可以创建以前在其他单材料平台上无法实现的通用量子器件。在这里，我们在MATBG中设计约瑟夫森结和隧道晶体管，仅由静电门定义。我们的多门控器件几何结构提供了对弱链接、屏障和隧道电极的独立控制。这些纯二维MATBG Josephson结在磁场中表现出非局部电动力学，与超薄超导体的Pearl理论一致。利用MATBG的本征带隙，我们还展示了在相同的MATBG器件内的单片边缘隧穿光谱，并测量了超导相MATBG的能谱。此外，通过诱导双势垒几何，器件可以像单电子晶体管一样工作，表现出库仑封锁。由于在单一材料中包含多种功能，这些MATBG隧道器件可以在基于石墨烯的可调谐超导量子比特，片上超导电路和电磁传感中找到应用。
Magic-angle twisted bilayer graphene exhibits a wide range of phases, such as metal, insulator and superconductor states. Now local electrostatic gating devices made from this two-dimensional material platform enable highly tunable Josephson junctions, edge tunnelling spectroscopy and single-electron transistor operation.Magic-angle twisted bilayer graphene (MATBG) has recently emerged as a highly tunable two-dimensional material platform exhibiting a wide range of phases, such as metal, insulator and superconductor states. Local electrostatic control over these phases may enable the creation of versatile quantum devices that were previously not achievable in other single-material platforms. Here we engineer Josephson junctions and tunnelling transistors in MATBG, solely defined by electrostatic gates. Our multi-gated device geometry offers independent control of the weak link, barriers and tunnelling electrodes. These purely two-dimensional MATBG Josephson junctions exhibit non-local electrodynamics in a magnetic field, in agreement with the Pearl theory for ultrathin superconductors. Utilizing the intrinsic bandgaps of MATBG, we also demonstrate monolithic edge tunnelling spectroscopy within the same MATBG devices and measure the energy spectrum of MATBG in the superconducting phase. Furthermore, by inducing a double-barrier geometry, the devices can be operated as a single-electron transistor, exhibiting Coulomb blockade. With versatile functionality encompassed within a single material, these MATBG tunnelling devices may find applications in graphene-based tunable superconducting qubits, on-chip superconducting circuits and electromagnetic sensing.