Tight-Binding Superconducting Phases in the Unconventional Compounds Strontium-Substituted Lanthanum Cuprate and Strontium Ruthenate

TL;DR

This paper employs a Wigner probability distribution approach within a tight-binding framework to predict and analyze multiple superconducting phases in strontium-substituted lanthanum cuprate and strontium ruthenate, revealing complex phase behaviors.

Contribution

It introduces a novel phenomenological method using Wigner distributions and tight-binding calculations to identify and differentiate phases in two unconventional superconductors.

Findings

Identified three phases in La2-xSrxCuO4, including antiferromagnetic, metallic, and strange metal phases.

Differentiated three phases in strontium ruthenate, including nodal, quasinodal, and mixed superconducting phases.

Provided a theoretical basis for comparing experimental data with numerical phase predictions.

Abstract

We use the idea of the Wigner probability distribution (WPD) in a reduced scattering phase space (RPS) for the elastic scattering cross-section, with the help of a Tight-Binding (TB) numerical procedure allowing us to consider the anisotropic quantum effects, to phenomenologically predict several phases in these two novel unconventional superconductors. Unlike our previous works with pieces of evidence that these two compounds are in the unitary strong scattering regime and that superconductivity is suppressed by the atoms of strontium in both materials, several phases are built. In the case of the strontium-substituted lanthanum cuprate, it was found three phases from one family of Wigner probabilistic distributions, one corresponding to the antiferromagnetic compound La2CuO4 another one which consists of a coalescing metallic phase for very lightly doped La2-xSrxCuO4, and finally a strong self-consistent dependent strange metal phase with optimal levels of doping. In the case of a triplet superconductor strontium ruthenate, three phases can be differentiated from two families of Wigner distribution probabilities, one family of WDP with point nodes where Cooper pairs and dressed scattered normal quasiparticles are mixed for the whole range of frequencies and which correspond to an FS $\gamma$ flat-sheet in the ground metallic state, and two phases from another WPD family, where, in one of then, the Miyake-Narikiyo quasinodal tiny gap model allows the unique presence of Cooper pairs in a tiny interval of frequencies near the superconducting transition TC, the other phase corresponds to the mixed-phase with Cooper pairs and dressed by stoichiometric strontium non-magnetic atoms, where strong self-consistent effects are noticeable. This approach allows comparing experimental results for samples in both compounds with numerical analysis studies.