First-Principles Correlated Approach to the Normal State of Strontium Ruthenate

S Acharya,Dibyendu Dey,T Maitra,A Taraphder,M S Laad

doi:10.1038/srep43033

Abstract

The interplay between multiple bands, sizable multi-band electronic correlations and strong spin-orbit coupling may conspire in selecting a rather unusual unconventional pairing symmetry in layered Sr2RuO4. This mandates a detailed revisit of the normal state and, in particular, the T-dependent incoherence-coherence crossover. Using a modern first-principles correlated view, we study this issue in the actual structure of Sr2RuO4 and present a unified and quantitative description of a range of unusual physical responses in the normal state. Armed with these, we propose that a new and important element, that of dominant multi-orbital charge fluctuations in a Hund’s metal, may be a primary pair glue for unconventional superconductivity. Thereby we establish a connection between the normal state responses and superconductivity in this system.

Highlights

IntroductionRu–4d xy, yz, zx bands, arise due to the complex interplay between orbital-selectivity and SOC
Motivated thereby, we undertake a correlated first-principles theoretical approach using a combination of density functional theory and dynamic mean-field theory (DFT +dynamical mean field theory (DMFT)) to address these issues
The high-T infra-red singularities in one- and two-particle propagators we find in DMFT are associated with local processes akin to those occurring in the seminal orthogonality catastrophe[21]

Summary

Introduction

Ru–4d xy, yz, zx bands, arise due to the complex interplay between orbital-selectivity and SOC. The implications of this on various proposals for the emergence of USC (from a correlated FL state in Sr2RuO4) are discussed. We perform Wannierization of the Wien2k output bands around the Fermi level via interface programs like WANNIER9013, WIEN2WANNIER14 This in turn, gives us the Wannier orbital-projected bands around the Fermi level which serve as inputs of the DMFT self-consistency calculation. It is clear that there is a sizable variation in the orbital character of the three t2g states as one traverses the Fermi pockets in momentum space: this is a consequence of the intricate interplay between inter-band mixing, modified to reflect spin-orbital entanglement in the band structure due to strong spin-orbit coupling (SOC). We argue in the subsequent sections that the Wannier orbitals having different bandwidths Wll, the effective Ull/Wll is different for different orbitals leading to self energies Σll which is different for each Wannier orbitals, does not require choice of an orbital specific anisotropic Ull at the first place

Methods

Results

Conclusion