Orbital-differentiated coherence-incoherence crossover identified by photoemission spectroscopy in LiFeAs

TL;DR

This study uses photoemission spectroscopy to reveal that in LiFeAs, the orbital-dependent quasiparticle anomalies are primarily driven by Hund's coupling, clarifying the physical origin of orbital differentiation in this superconductor.

Contribution

The paper provides direct experimental evidence linking Hund's coupling to orbital differentiation in LiFeAs, supported by first-principles many-body theory calculations.

Findings

Orbital-dependent quasiparticle lifetime anomalies identified.

Strong agreement between experiment and theory confirms Hund's coupling role.

Clarifies the physical origin of orbital differentiation in FeSCs.

Abstract

In the iron-based superconductors (FeSCs), orbital differentiation is an important phenomenon, whereby correlations stronger on the dxy orbital than on the dxz/yz orbital yield quasi-particles with dxy} orbital character having larger mass renormalization and abnormal temperature evolution. However, the physical origin of this orbital differentiation is debated between the Hund's coupling induced unbinding of spin and orbital degrees of freedom and the Hubbard interaction instigated orbital selective Mott transition. Here we use angle-resolved photoemission spectroscopy to identify an orbital-dependent correlation-induced quasi-particle (QP) anomaly in LiFeAs. The excellent agreement between our photoemission measurements and first-principles many-body theory calculations shows that the orbital-differentiated QP lifetime anomalies in LiFeAs are controlled by the Hund's coupling.