Unconventional Iron-Based Superconductor CsCa2Fe4As4F2: A First-Principle Study

In the present work, we have investigated the structural and electronic properties of newly discovered iron based superconductor CsCa2Fe4As4F2 using first principles calculations. Analysis of the density of states at the Fermi level suggests that Fe-3d states have dominating contribution, and within these 3d states contribution of e(g) states is significant suggesting multi-band nature of this superconductor. The upper bound of superconducting transition temperature, estimated using electron-phonon coupling constant is found to be similar to 2.6 K. To produce the experimental value of transition temperature (28.2 K), a 4-5 times increase in the electron-phonon constant is necessary, hinting that conventional electron-phonon coupling is not enough to explain the origin of superconductivity.