A layering model for superconductivity in the borocarbides

TL;DR

This paper introduces a layered superlattice model to explain superconductivity in borocarbides, capturing their electronic properties through a simplified one-dimensional approach with local interactions and band offsets.

Contribution

It presents a novel superlattice model that systematically describes superconductivity across the borocarbide family using a minimal multi-band framework.

Findings

Model reproduces metallic and superconducting states.

Numerical analysis shows charge gap and pairing correlations.

Systematic parametrization of borocarbides' electronic ground states.

Abstract

We propose a superlattice model to describe superconductivity in layered materials, such as the borocarbide families with the chemical formul\ae\ $RT_2$B$_2$C and $RT$BC, with $R$ being (essentially) a rare earth, and $T$ a transition metal. We assume a single band in which electrons feel a local attractive interaction (negative Hubbard-$U$) on sites representing the $T$B layers, while U=0 on sites representing the $R$C layers; the multi-band structure is taken into account minimally through a band offset $\epsilon$. The one-dimensional model is studied numerically through the calculation of the charge gap, the Drude weight, and of the pairing correlation function. A comparison with the available information on the nature of the electronic ground state (metallic or superconducting) indicates that the model provides a systematic parametrization of the whole borocarbide family.