Orbital selectivity versus Pomeranchuk instability in the iron-chalcogenide superconductors: A two-loop renormalization group study

TL;DR

This study uses a two-loop renormalization group approach to analyze a multiband model relevant for iron-chalcogenide superconductors, highlighting the role of orbital selectivity over Pomeranchuk instability in nematicity.

Contribution

It introduces higher-order RG calculations including self-energy effects, emphasizing orbital selectivity as the origin of nematicity in iron-chalcogenides.

Findings

Orbital selectivity may drive nematicity instead of Pomeranchuk instability.

Stripe-type antiferromagnetic fluctuations promote orbital-selective effects.

Results suggest a weak-to-moderate coupling scenario for superconductivity.

Abstract

We perform a two-loop renormalization group (RG) analysis of a 2D effective multiband model, which is relevant for describing the low-energy properties of some iron-chalcogenide superconducting materials. Crucial ingredients in this analysis are the calculation of higher-order contributions in the RG scheme that go beyond the widely-used parquet approximation and the consequent inclusion of nontrivial self-energy effects of the model that yield an anisotropic renormalization of the quasiparticle weight in the system. The motivation of our work is the experimental discovery by Sprau et al. (2017) that orbitally-selective renormalization of the quasiparticle weight in the Hund's metal phase at moderate temperatures underpins the highly unusual gap in the superconducting phase of the FeSe compound at lower temperatures. One prediction we arrive here is that the underlying origin of nematicity in these systems may indeed come from orbital-selectivity, instead of a Pomeranchuk instability in the $d_{\pm}$ channel. This orbital selectivity is driven by the presence of stripe-type antiferromagnetic fluctuations in the model. Therefore, we argue that the present RG results may provide a scenario from a weak-to-moderate coupling perspective, in which the role of orbital selectivity to describe the physical properties of some iron-chalcogenide superconductors is emphasized.