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 [ Time:2019/3/11 ]
Scientists Reveal Mechanism of Lifshitz Transition in Electron-doped Iron Selenides
Author :LIU Dayong

A Chinese joint team revealed a mechanism of Lifshitz transition in electron-doped iron selenides.

High-temperature superconductors (mainly including copper-based and iron-based superconductors) have always been at the forefront of condensed matter physics research due to their attractive application prospects.

In recent years, iron selenides of iron-based superconductors have also raised great interest due to their high superconducting transition temperature (Tc).

However, the key factor for the high Tc is still under debate, and the correlated electronic structure is the first step to address this issue.

The iron-selenides (Li1-xFex)OHFeSe, which has Tc ~ 40 K, much higher than Tc ~ 8 K of pure FeSe, is an important reference material due to the absence of Fe vacancies and its novel electronic structure with only electronic pockets.

Unfortunately, there are still some discrepancies between different experiments and theoretical calculations in the electronic structure of (Li1-xFex)OHFeSe.

In the recent study, the joint team investigated the correlated electronic structure of electron-doped iron-selenides (Li1-xFex)OHFeSe.

In view of the inconsistency in the electronic structure of ARPES and STM experiments and DFT calculations in electron-doped iron-selenides, the researchers further combined DFT and dynamical mean-field theory (DMFT) implemented with continuous-time quantum Monte Carlo (CT-QMC) impurity solver to explore the influence of electronic correlation and spin-orbit coupling (SOC) on the electronic structure of (Li1-xFex)OHFeSe based on previous work (New J. Phys. 19, 023028 (2017)).

They found a correlation-driven Lifshitz transition from FeSe to the heavily electron-doped compound (Li0.8Fe0.2)OHFeSe (as shown in Fig. 1).

Moreover, the SOC also considerably induced a gap in the Dirac dispersion around point.

These results were in good agreement with the experimental data, which demonstrated the many-body characteristics.

These correlation-driven electronic structures enriched the understanding of Fermi surface topology, suggesting a quite distinct superconducting state of (Li0.8Fe0.2)OHFeSe in comparison with bulk FeSe.

This work was supported by the National Science Foundation of China under Grants No. 11574315, No. 11190022, No. 11404172, and No. 11474287 and the Key Research Program of the Chinese Academy of Sciences (Grant No. XDPB01). Numerical calculations were performed at the Center for Computational Science of CASHIPS and the ScGrid of Supercomputing Center and Computer Network Information Center of the Chinese Academy of Sciences.

Link to the paper: Correlation-driven Lifshitz transition in electron-doped iron selenides (Li,Fe)OHFeSe

Figure 1. Momentum-resolved spectral function of (Li1-xFex)OHFeSe without (with) spin-orbit coupling within DFT + DMFT. (mage by LIU Dayong)

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