Whether the newly discovered KxFe2-ySe2 systems are doped Mott or band insulators is key to how superconductivity emerges at lower temperature. With extant theoretical studies supporting conflicting scenarios, a more realistic approach is urgently called for. Here, we use LDA+DMFT to study this issue in KxFe2-ySe2. We find that the undoped KFe1.6Se2 system is a new kind of Mott-Kondo insulator (MKI). Electron doping this MKI drives a Mott transition to an orbital-selective non-Fermi liquid metal. Good agreement with spectral and transport responses supports our view, implying that superconductivity arises from a doped Mott insulator, as in the high-Tc cuprates.
@article{arxiv.1109.0116,
title = {Unconventional Mott Transition in KxFe2-ySe2},
author = {L. Craco and M. S. Laad and S. Leoni},
journal= {arXiv preprint arXiv:1109.0116},
year = {2015}
}