Superconducting Properties of MXene Monolayers
Abstract: MXenes are a new class of two-dimensional materials, consisting of a carbon or nitrogen layer sandwiched in between two transition metal layers. Various experimental studies have demonstrated that these crystals have broad and growing areas of application, such as Li-ion batteries, super-capacitors, fuel-cells and hydrogen storage. Since most of the MXene monolayers are metals, they could also host superconductivity, depending on their electronic and vibrational properties. Therefore, we have systematically investigated the superconducting properties of monolayer MXenes of stoichiometry M2X (M being the transition metal and X either C or N), with a first-principles approach to Eliashberg theory. Due to the presence of the transition metal, we found the choice of the type of exchange- correlation and inclusion of spin-orbit interactions to be crucial to describe the vibrational and superconducting properties of these monolayers. Cautiously considering these, we have identified five new superconducting monolayer MXenes, out of which three carbides (Mo2C, W2C and Sc2C) and two nitrides (Mo2N and Ta2N). The highest predicted critical temperature (Tc) of 17 K is found for Mo2N. Our first principle-based systematic analysis clearly has opened up a whole new class of superconductors with sizeable Tc in the monolayer limit.