Temperature-induced band selective localization and coherent-incoherent crossover in single-layer FeSe/Nb:BaTiO3 /KTaO3

TL;DR

This study uses photoemission spectroscopy to reveal temperature-dependent band selective localization and a crossover from coherent to incoherent electronic states in single-layer FeSe on various substrates, shedding light on electron correlations.

Contribution

It demonstrates temperature-induced band selective localization and coherent-incoherent crossover in single-layer FeSe, advancing understanding of electron correlations in iron chalcogenide superconductors.

Findings

Band selective localization occurs with increasing temperature.

Spectral weight of incoherent background increases with temperature.

Signatures of polaronic behavior indicate electron-boson interactions.

Abstract

Iron chalcogenide superconductors are multi-band systems with strong electron correlations. Here we use angle-resolved photoemission spectroscopy to study band dependent correlation effects in single-layer FeSe/Nb:BaTiO3/KTaO3, a new iron chalcogenide superconductor with non-degenerate electron pockets and interface-enhanced superconductivity. The non-degeneracy of the electron bands helps to resolve the temperature dependent evolution of different bands. With increasing temperature, the single layer FeSe undergoes a band-selective localization, in which the coherent spectral weight of one electron band is completely depleted while that of the other one remains finite. In addition, the spectral weight of the incoherent background is enhanced with increasing temperature, indicating a coherent-incoherent crossover. Signatures of polaronic behavior are observed, suggesting electron-boson interactions. These phenomena help to construct a more complete picture of electron correlations in the FeSe family.