Electronic orders near the type-II van Hove singularity in BC$_3$

TL;DR

This study uses the functional renormalization group to explore electron instabilities in BC$_3$ near a type-II van Hove singularity, revealing potential for topological p+ip' superconductivity.

Contribution

It demonstrates the dominance of ferromagnetic-like order near the singularity and p-wave superconductivity elsewhere, highlighting BC$_3$ as a candidate for topological superconductivity.

Findings

Ferromagnetic-like spin density wave order dominates near the singularity.

p-wave superconductivity prevails away from the singularity.

Small Coulomb repulsion enhances superconductivity.

Abstract

Using the functional renormalization group, we investigate the electron instability in the single-sheet BC$_3$ when the electron filling is near a type-II van Hove singularity. For a finite Hubbard interaction, the ferromagnetic-like spin density wave order dominates in the immediate vicinity of the singularity. Elsewhere near the singularity the p-wave superconductivity prevails. We also find that a small nearest-neighbor Coulomb repulsion can enhance the superconductivity. Our results show that BC$_3$ would be a promising candidate to realize topological $p+ip'$ superconductivity, but the transition temperature is practically sizable only if the local interaction is moderately strong.