paper

Correlation strength, Lifshitz transition and the emergence of a two- to three-dimensional crossover in FeSe under pressure

arXiv:1802.01850 · doi:10.1103/PhysRevB.97.115165

Abstract

We report a detailed theoretical study of the electronic structure, spectral properties, and lattice parameters of bulk FeSe under pressure using a fully charge self-consistent implementation of the density functional theory plus dynamical mean-field theory method (DFT+DMFT). In particular, we perform a structural optimization and compute the evolution of the lattice parameters (volume, ratio, and the internal position of Se) and the electronic structure of the tetragonal (space group ) paramagnetic FeSe. Our results for the lattice parameters are in good quantitative agreement with experiment. The ratio is slightly overestimated by about ~\%, presumably due to the absence of the van der Waals interactions between the FeSe layers in our calculations. The lattice parameters determined within DFT are off the experimental values by a remarkable -~\%, implying a crucial importance of electron correlations. Upon compression to ~GPa, the ratio and the lattice volume show a decrease by and ~\%, respectively, while the Se coordinate weakly increases by ~\%. Most importantly, our results reveal a topological change of the Fermi surface (Lifshitz transition) which is accompanied by a two- to three-dimensional crossover. Our results indicate a small reduction of the quasiparticle mass renormalization by about ~\% for the and less than ~\% for the states, as compared to ambient pressure. The behavior of the momentum-resolved magnetic susceptibility shows no topological changes of magnetic correlations under pressure, but demonstrates a reduction of the degree of the in-plane stripe-type nesting. Our results for the electronic structure and lattice parameters of FeSe are in good qualitative agreement with recent experiments on its isoelectronic counterpart FeSeS.

10 pages, 6 figures

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