Evolution from incoherent to coherent electronic states and its implications to superconductivity in FeTe1-xSex

TL;DR

This study uses ARPES to investigate how electronic coherence in FeTe1-xSex evolves with composition, revealing that increased coherence correlates with the onset of superconductivity.

Contribution

It demonstrates the transition from incoherent to coherent electronic states as a key factor in the emergence of superconductivity in FeTe1-xSex.

Findings

Incoherent electronic states at x=0 with small quasiparticle weight.

Progressive sharpening of spectral features with increasing x.

Emergence of well-defined quasiparticles around x=0.45 coinciding with superconductivity.

Abstract

We have performed systematic angle-resolved photoemission spectroscopy (ARPES) of iron-chalcogenide superconductor FeTe1-xSex to elucidate the electronic states relevant to the superconductivity. While the Fermi-surface shape is nearly independent of x, we found that the ARPES spectral line shape shows prominent x dependence. A broad ARPES spectrum characterized by a small quasiparticle weight at x = 0, indicative of incoherent electronic states, becomes progressively sharper with increasing x, and a well-defined quasiparticle peak appears around x = 0.45 where bulk superconductivity is realized. The present result suggests the evolution from incoherent to coherent electronic states and its close relationship to the emergence of superconductivity.