# Effects of strain on the electronic structure, superconductivity, and nematicity in FeSe studied by angle-resolved photoemission spectroscopy

## TL;DR

This study uses angle-resolved photoemission spectroscopy to show how strain alters the electronic structure and nematicity in FeSe, significantly impacting its superconducting transition temperature (T_c).

## Contribution

It reveals that in-plane strain modifies the band overlap and Fermi surface, linking structural changes to superconductivity and nematicity in FeSe.

## Key findings

- Strain causes a significant change in the energy overlap between hole and electron pockets.
- Alteration in band overlap correlates with changes in T_c.
- Nematicity strength is characterized by the band overlap DeltaE_{h-e}.

## Abstract

One of central issues in iron-based superconductors is the role of structural change to the superconducting transition temperature (T_c). It was found in FeSe that the lattice strain leads to a drastic increase in T_c, accompanied by suppression of nematic order. By angle-resolved photoemission spectroscopy on tensile- or compressive-strained and strain-free FeSe, we experimentally show that the in-plane strain causes a marked change in the energy overlap (DeltaE_{h-e}) between the hole and electron pockets in the normal state. The change in DeltaE_{h-e} modifies the Fermi-surface volume, leading to a change in T_c. Furthermore, the strength of nematicity is also found to be characterized by DeltaE_{h-e}. These results suggest that the key to understanding the phase diagram is the fermiology and interactions linked to the semimetallic band overlap.