Correlation-driven Lifshitz transition in electron-doped iron selenides (Li,Fe)OHFeSe

Effects of electronic correlation and spin-orbit coupling (SOC) on electronic structure of iron selenides (Li1-xFex)OHFeSe have been investigated with the combination of density functional theory (DFT) and dynamical mean-field theory. It is found that the electronic correlation substantially changes the Fermi surface topology for x = 0.2, resulting in a tiny electron pocket around the zone center Gamma and two large electron pockets around the zone corner M, respectively. Moreover, the SOC also considerably affects the low-energy electronic structure near the Fermi level, especially inducing a gap in the Dirac-like dispersion around Gamma for x = 0.2. Our calculations show a correlation-driven Lifshitz transition from FeSe to the heavily electron-doped compound, leading to a transition of the nesting wave vector from (pi, 0) to (pi, 0.57 pi +/- delta) accompanied by an orbital-weight redistribution between the d(xy) and d(xz)/d(yz), orbitals. These correlation-driven electronic structures enrich the understanding of different DFT and experimental results, suggesting a quite distinct superconducting state of (Li0.8Fe0.2)OHFeSe in comparison with FeSe.