Revealing the Empty-State Electronic Structure of Single-Unit-Cell FeSe/SrTiO$_{3}$

TL;DR

This study uses scanning tunneling spectroscopy and quasiparticle interference imaging to explore the electronic structure of single-unit-cell FeSe on SrTiO3, revealing new empty-state features and their orbital characteristics.

Contribution

It introduces a combined experimental and theoretical approach to map and understand the empty electronic states in FeSe/SrTiO3, highlighting the role of Se height in tuning these states.

Findings

Discovery of a $\Gamma$-centered electron pocket 75 meV above Fermi level

Identification of the orbital nature of empty states at $\Gamma$

Se height as a key parameter influencing electronic properties

Abstract

We use scanning tunneling spectroscopy to investigate the filled and empty electronic states of superconducting single-unit-cell FeSe deposited on SrTiO$_3$(001). We map the momentum-space band structure by combining quasiparticle interference imaging with decay length spectroscopy. In addition to quantifying the filled-state bands, we discover a $\Gamma$-centered electron pocket 75 meV above the Fermi energy. Our density functional theory calculations show the orbital nature of empty states at $\Gamma$ and suggest that the Se height is a key tuning parameter of their energies, with broad implications for electronic properties.