IDEAL DIAMAGNETIC RESPONSE OF A PRISTINE GRAPHENE-n-HEPTANE-PERMALLOY SYSTEM

We explored magnetic screening of milligauss fields in a system comprised of a single-layer graphene (on various substrates) wetted by n-heptane in the presence of a thin Fe-Ni foil parallel to the graphene layer. Our initial task was to confirm the results and find the origins of ideal diamagnetic screening reported previously in [Y. Kawashima, arXiv:cond-mat/1801.09376]. Indeed, we obtained ideal diamagnetic response. Also, in some cases “paramagnetic Meissner effect” has been obtained which in case of superconducting origin of observed facts can be associated with Wohlleben effect. At the same time, a crucial dependence of humidity and possibly other atmospheric factors on results has been observed which can be explained by chemisorption described in e.g. [T.L. Burnett et.al., arXiv:1204.3323]. These factors completely inhibit both normal and negative diamagnetism. To minimize this effect experiments were performed in Ar atmosphere. This may or may not be a footprint of superconductivity at room temperature. In both cases understanding the signal under different conditions may spread a light on a yet unknown phenomenon in condensed matter physics.