Solid MgB2 has rather interesting and technologically important properties, such as a very high superconducting transition temperature. Focusing on this compound, we report the first nontrivial application of a novel density-functional-type theory for superconductors, recently proposed by the authors. Without invoking any adjustable parameters, we obtain the transition temperature, the gaps, and the specific heat of MgB2 in very good agreement with experiment. Moreover, our calculations show how the Coulomb interaction acts differently on σ and π states, thereby stabilizing the observed super-conducting phase.
Bibliographical noteFunding Information:
The authors thank Giovanni Ummarino for helpful discussions and for providing results from Eliashberg calculations. This work was supported by the Italian MIUR under the projects PRIN 2006021741 and PON-CyberSar, by the Deutsche Forschungsgemeischaft within the program SPP 1145, by the EXC!TiNG Research and Training Network of the European Union, and by the NANOQUANTA NOE. We also acknowledge financial support by INFM (through a computing grant at Cineca, Bologna, Italy).