Silicene and Germanene as prospective playgrounds for Room Temperature Superconductivity

Abstract

Combining theory and certain striking phenomenology we suggest that silicene and germanene are \textit{elemental Mott insulators} and abode of doping induced high Tc superconductivity. In our theory, a 3 fold reduction in silicene $\pi - \pi^*$ band width, in comparison to graphene, and short range coulomb interactions enable Mott localization. Recent experimental results are invoked to provide support for our Mott insulator model: i) a significant $\pi$-band narrowing, in silicene on ZrB$_2$ seen in ARPES, ii) a superconducting gap appearing below 35 K with a large $\frac{2\Delta}{k_BTc}\sim$ 20 in silicene on Ag, iii) emergence of electron like pockets at M points, on electron doping by Na adsorbent, iv) certain coherent quantum oscillation like features exhibited by silicene transistor at room temperatures and v) absence of Landau level splitting upto 7 Tesla and vi) superstructures, not common in graphene but, ubiquitous in silicene. A synthesis of the above results using theory of Mott insulator, with and without doping, is attempted. We surmise that if competing orders are taken care of and optimal doping achieved, superconductivity in silicene and germanene could reach room temperature scales; our estimates of model parameters, t and J $\sim$ 1 eV, are encouragingly high, compared to cuprates.