Abstract
The Josephson current is investigated in a superconducting graphene bilayer where pristine graphene sheets can make in-plane or out-of-plane displacements with respect to each other. The superconductivity can be of an intrinsic nature, or due to a proximity effect. The results demonstrate that the supercurrent responds qualitatively differently to relative displacement if the superconductivity is due to either intralayer or interlayer spin-singlet electron-electron pairing, thus providing a tool to distinguish between the two mechanisms. Specifically, both the AA and AB stacking orders are studied with antiferromagnetic spin alignment. For the AA stacking order with intralayer and on-site pairing no current reversal is found. In contrast, the supercurrent may switch its direction as a function of the in-plane displacement and out-of-plane interlayer coupling for the cases of AA ordering with interlayer pairing and AB ordering with either intralayer or interlayer pairing. In addition to sign reversal, the Josephson signal displays many characteristic fingerprints which derive directly from the pairing mechanism. Thus, measurements of the Josephson current as a function of the graphene bilayer displacement open up the means achieve deeper insights into the superconducting pairing mechanism.
Highlights
Two-dimensional materials have attracted enormous attention during the last decade
The results demonstrate that the supercurrent responds qualitatively differently to relative displacement if the superconductivity is due to either intralayer or interlayer spin-singlet electron-electron pairing, providing a tool to distinguish between the two mechanisms
The experimental phenomenology in twisted bilayer graphene (tBLG) is similar to the high-Tc superconductivity observed in cuprates, and the putative displacement- or twist-induced d-wave symmetry in tBLG might offer some useful hints towards the cuprate problem
Summary
Two-dimensional materials have attracted enormous attention during the last decade. One of the main reasons is the unique opportunity to make these materials thinner down to atomic mono- or bilayers [1,2], and the possibility of a subsequent stacking of the constituents at an essentially arbitrary relative displacement or twist angle that results in qualitative consequences on the microscopic and macroscopic properties of the system. Josephson effect in graphene bilayers with adjustable relative displacement The results demonstrate that the supercurrent responds qualitatively differently to relative displacement if the superconductivity is due to either intralayer or interlayer spin-singlet electron-electron pairing, providing a tool to distinguish between the two mechanisms.
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