Temperature evolution of the Fermi surface of the FeSe monolayer on SrTiO$_3$

TL;DR

This study reveals that the Fermi surface of FeSe monolayer on SrTiO$_3$ remains nearly unchanged across temperatures, contrasting with bulk FeSe, and provides insights into its superconductivity mechanism.

Contribution

It uncovers the temperature independence of the Fermi surface in FeSe monolayer, highlighting its unique electronic structure compared to bulk FeSe.

Findings

Fermi surface remains nearly constant over temperature range

Contrasts with temperature-dependent Fermi surface in bulk FeSe

Provides clues to the superconductivity mechanism in monolayer FeSe

Abstract

The origin of superconductivity in the FeSe monolayer on SrTiO$_3$ remains one of the unresolved mysteries in condensed-matter physics. Here by investigation of the temperature evolution of the dynamic charge response of FeSe/SrTiO$_3$ we infer that the response of the monolayer itself is nearly temperature independent. This indicates a constant Fermi surface over a wide range of temperature, in stark contrast to that of the bulk FeSe and other Fe-based superconductors. Our results, which manifest the peculiarity of the electronic structure of the FeSe monolayer, may help for a microscopic understanding of the superconductivity in Fe-chalcogenide monolayers on oxide surfaces in general.