Chapman J, Su Y, Howard C A, Kundys D, Grigorenko A N, Guinea F, Geim A K, Grigorieva I V, Nair R R
School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.
Department of Physics and Astronomy, University College London, London, WC1E 6BT, UK.
Sci Rep. 2016 Mar 16;6:23254. doi: 10.1038/srep23254.
Despite graphene's long list of exceptional electronic properties and many theoretical predictions regarding the possibility of superconductivity in graphene, its direct and unambiguous experimental observation has not been achieved. We searched for superconductivity in weakly interacting, metal decorated graphene crystals assembled into so-called graphene laminates, consisting of well separated and electronically decoupled graphene crystallites. We report robust superconductivity in all Ca-doped graphene laminates. They become superconducting at temperatures (Tc) between ≈4 and ≈6 K, with Tc's strongly dependent on the confinement of the Ca layer and the induced charge carrier concentration in graphene. We find that Ca is the only dopant that induces superconductivity in graphene laminates above 1.8 K among several dopants used in our experiments, such as potassium, caesium and lithium. By revealing the tunability of the superconducting response through doping and confinement of the metal layer, our work shows that achieving superconductivity in free-standing, metal decorated monolayer graphene is conditional on an optimum confinement of the metal layer and sufficient doping, thereby bringing its experimental realization within grasp.
尽管石墨烯具有一系列卓越的电子特性，且有许多关于石墨烯中超导可能性的理论预测，但尚未实现其直接且明确的实验观测。我们在组装成所谓石墨烯层压板的弱相互作用、金属修饰的石墨烯晶体中寻找超导性，这些层压板由分离良好且电子解耦的石墨烯微晶组成。我们报告了所有钙掺杂石墨烯层压板中都存在稳健的超导性。它们在约4至约6 K的温度（Tc）下转变为超导态，Tc强烈依赖于钙层的限制以及石墨烯中诱导的载流子浓度。我们发现，在我们实验中使用的几种掺杂剂（如钾、铯和锂）中，钙是唯一能在高于1.8 K的石墨烯层压板中诱导超导性的掺杂剂。通过揭示通过掺杂和金属层限制来调节超导响应，我们的工作表明，在独立的、金属修饰的单层石墨烯中实现超导性取决于金属层的最佳限制和足够的掺杂，从而使其实验实现指日可待。
