Superconductivity in an Al-twisted bilayer graphene-Al junction device

Abstract

We report on realization and quantum transport study of a twisted bilayer graphene (tBLG) Josephson junction device. High-quality tBLG employed in the device fabrication is obtained via chemical vapour deposition and the device is fabricated by contacting a piece of tBLG by two closely spaced Al electrodes in an Al-tBLG-Al Josephson junction configuration. Low-temperature transport measurements show that below the critical temperature of the Al electrodes (T c ≈ 1.1 K), the device exhibits sizable supercurrents at zero magnetic field, arising from the superconducting proximity effect with high contact transparency in the device. In the measurements of the critical supercurrent as a function of perpendicularly applied magnetic field, a standard Fraunhoferlike pattern of oscillations is observed, indicating a uniform supercurrent distribution inside the junction. Multiple Andreev reflection characteristics are also observed in the spectroscopy measurements of the device, and their magnetic field and temperature dependencies are found to be well described by the Bardeen−Cooper−Schrieffer theory. arXiv:2003.02577v1 [cond-mat.mes-hall]

A review of experimental advances in twisted graphene moiré superlattice*

“…[73,74] Currently, owning to the high sensitivity of the band structure to the twist angle and a limited spatial resolution of some techniques such as ARPES, a lack of large and uniform sample still stands in the way of development of twistronics. Chemical vapor deposition, by which random twist angle and 30 • twisted bilayer graphene quasicrystals have been achieved, [75][76][77][78] improved mechanical exfoliation method, [79,80] direct bonding, [81] and tip-assisted twist angle manipulation [3,74] are some potential solutions, yet technical challenges like angle control remain and more efforts are expected in the future.…”

Enhanced Hetero‐Junction Quality and Performance of Kesterite Solar Cells by Aluminum Hydroxide Nanolayers and Efficiency Limitation Revealed by Atomic‐resolution Scanning Transmission Electron Microscopy

“…[3,[58][59][60][61] The origin is assumed to be related to Kirkendall effect due to the different diffusion rate of constituents, e.g., Cu has higher diffusivity than other elements and tends to diffuse through the bulk to the surface to react with S/Se, thus leaving behind vacancies that facilitate other elements diffusion to the surface, and finally voids are formed in the bulk or in the absorber/Mo interface. [59,[62][63][64] Additionally, for kesterite solar cells, the detrimental reaction between CZTSSe and Mo and the volatile Sn chalcogenides loss during elevated reaction temperatures are also considered as possible reasons. [65,66] The voids near the CZTSSe/Mo interface clearly influence the mechanical properties like adhesion between absorbers and Mo.…”