# Lifted electron pocket and reversed orbital occupancy imbalance in FeSe

## TL;DR

This study uses advanced spectroscopy to clarify the electronic structure of FeSe in its nematic phase, revealing a reversed orbital imbalance and absence of a Fermi pocket, thus resolving previous controversies.

## Contribution

It provides the first detailed orbital-resolved band structure of FeSe, clarifying the nature of its nematic phase and resolving conflicting experimental results.

## Key findings

- Absence of a Fermi pocket at the Y point in FeSe.
- Reversed orbital occupancy imbalance compared to iron pnictides.
- Identification of band dispersions with orbital characters near the Brillouin zone corner.

## Abstract

The FeSe nematic phase has been the focus of recent research on iron based superconductors (IBSs) due to its unique properties. A number of electronic structure studies were performed to find the origin of the phase. However, such attempts came out with conflicting results and caused additional controversies. Here, we report results from angle resolved photoemission and X-ray absorption spectroscopy studies on FeSe with detwinning by a piezo stack. We have fully resolved band dispersions with orbital characters near the Brillouin zone corner which reveals absence of a Fermi pocket at the Y point in the 1Fe Brillouin zone. In addition, the occupation imbalance between dxz and dyz orbitals is found to be opposite to that of iron pnictides, which is consistent with the identified band characters. These results settle down controversial issues in the FeSe nematic phase and shed light on the origin of nematic phases in IBSs.