# Role of electric fields on enhanced electron correlation in surface-doped FeSe

## TL;DR

This study reveals how electric fields from potassium doping influence electron correlation in surface-doped FeSe by modifying atomic interactions and band structures, providing insights into high-temperature superconductivity mechanisms.

## Contribution

It demonstrates the impact of local electric fields on electron correlation in FeSe, highlighting the orbital-dependent effects and the role of Se height modifications.

## Key findings

- Electric fields weaken Se-mediated hopping between Fe d orbitals.
- Reduction in hopping narrows Fe d bands, enhancing electron correlation.
- Potassium doping increases Se height, further boosting correlation.

## Abstract

Electron-doped high-Tc FeSe reportedly has a strong electron correlation that is enhanced with doping. It has been noticed that significant electric fields exist inevitably between FeSe and external donors along with electron transfer. However, the effects of such fields on electron correlation are yet to be explored. Here we study potassium- (K-) dosed FeSe layers using density-functional theory combined with dynamical mean-field theory to investigate the roles of such electric fields on the strength of the electron correlation. We find, very interestingly, the electronic potential-energy difference between the topmost Se and Fe atomic layers, generated by local electric fields of ionized K atoms, weakens the Se-mediated hopping between Fe d orbitals. Since it is the dominant hopping channel in FeSe, its reduction narrows the Fe d bands near the Fermi level, enhancing the electron correlation. This effect is orbital dependent and occurs in the topmost FeSe layer only. We also find the K dosing may increase the Se height, enhancing the electron correlation further. These results shed new light on the comprehensive study of high-Tc FeSe and other low-dimensional systems.