Emergence of the nematic electronic state in FeSe

TL;DR

This study investigates the nematic electronic state in FeSe, revealing a transition driven by orbital-charge ordering with significant Fermi surface deformation and increased nematic susceptibility, using ARPES, quantum oscillations, and elastoresistance measurements.

Contribution

It provides a detailed experimental characterization of the nematic transition in FeSe, highlighting its electronically driven nature and the evolution of the Fermi surface across the structural transition.

Findings

Fermi surface deforms from four-fold to two-fold symmetry below 87 K

Nematic susceptibility increases sharply near the transition

Electronic structure changes cannot be explained solely by lattice effects

Abstract

We present a comprehensive study of the evolution of the nematic electronic structure of FeSe using high resolution angle-resolved photoemission spectroscopy (ARPES), quantum oscillations in the normal state and elastoresistance measurements. Our high resolution ARPES allows us to track the Fermi surface deformation from four-fold to two-fold symmetry across the structural transition at ~87 K which is stabilized as a result of the dramatic splitting of bands associated with dxz and dyz character. The low temperature Fermi surface is that a compensated metal consisting of one hole and two electron bands and is fully determined by combining the knowledge from ARPES and quantum oscillations. A manifestation of the nematic state is the significant increase in the nematic susceptibility as approaching the structural transition that we detect from our elastoresistance measurements on FeSe. The dramatic changes in electronic structure cannot be explained by the small lattice effects and, in the absence of magnetic fluctuations above the structural transition, points clearly towards an electronically driven transition in FeSe stabilized by orbital-charge ordering.