Spin-triplet superconductivity from interband effect in doped insulators

TL;DR

This paper introduces a new mechanism for spin-triplet superconductivity in multi-band systems, driven by interband interactions and electronic repulsion, with implications for materials like ZrNCl and WTe2.

Contribution

It proposes a general, analytically controlled theory for spin-triplet pairing via interband effects in doped insulators, supported by model calculations and experimental comparisons.

Findings

Identifies a non-retarded pairing mechanism mediated by interband transitions.

Suggests ZrNCl and WTe2 are likely spin-triplet superconductors.

Provides a theoretical framework applicable to doped band insulators.

Abstract

Despite being of fundamental importance and potential interest for topological quantum computing, spin-triplet superconductors remain rare in solid state materials after decades of research. In this work, we present a general mechanism for spin-triplet superconductivity in multi-band systems, where a non-retarded pairing interaction between conduction electrons is produced by their electronic repulsion to a third-electron undergoing a virtual interband transition. Our theory is analytically controlled by an interband hybridization parameter, and explicitly demonstrated in doped band insulators with the example of an extended Hubbard model. In light of this theory, we propose that recently discovered dilute superconductors such as ZrNCl and WTe$_2$ are spin-triplet, and compare the expected consequences of our theory with experimental data.