Superconductivity in novel surface and interface electronic systems

点击翻译按钮获取中文摘要

The possibility to tailor correlated interface and surface systems opens a wide range of novel and complex electronic behavior, including new fascinating examples of superconductivity. Recent cases are the superconductivity around 300mK in oxide heterostructures [1, 2] or the high-temperature interface superconductivity between insulating and metallic lanthanum copper oxides [3]. Apparently, the combination of two material systems not only allows to access previously unexplored parameter regions - such as high-mobility low-density electron gases in heterostructures - but can also give rise to many-body states not found in the separate constituent materials - such as the observed superconductivity. This raises the question whether one can think of new examples and possibly also of new physical mechanisms of superconductivity in such inhomogeneous situations that could lead to higher transition temperatures or other improvements such as higher critical current densities.In order to pursue these questions further, theoretical methods developed for bulk or isolated two-dimensional (2D) problems have to be adapted for the new systems. Here we plan to accomplish this for two modern and powerful theoretical frameworks: (i) the self-energy functional approach (SFA) for strongly correlated electrons, evaluated within the variational cluster approximation (VCA), and (ii) the functional renormalization group (fRG) for weak to moderate interactions for the study of long-range ordering tendencies. With these resources at hand, we plan to search for novel occurrences and mechanisms of superconductivity in heterostructures, surface systems and other layered structures. In particular, we plan to scrutinize two recent theoretical proposals in this context, and aim to come up with additional ideas for realizations of novel, possibly high-temperature superconductivity.