Chiral skyrmionic superconductivity from doping a Chern Ferromagnet

TL;DR

This paper demonstrates that doping a Chern ferromagnet can induce chiral superconductivity characterized by skyrmionic spin textures and chiral f-wave pairing, revealing a new microscopic mechanism potentially relevant for MoTe2 moiré superlattices.

Contribution

It introduces a novel mechanism for chiral superconductivity arising from skyrmion Cooper pairs in doped Chern ferromagnets, supported by exact diagonalization and DMRG calculations.

Findings

Cooper pairs formed by magnons and holes are stabilized at strong interactions and large Ising SOC.

The Cooper pairs exhibit finite spin chirality and chiral f-wave symmetry.

Interactions between skyrmion Cooper pairs change from repulsive to attractive with increasing SOC.

Abstract

We show that chiral superconductivity can be stabilized by hole doping a Chern ferromagnet. Performing exact diagonalization and density-matrix-renormalization-group calculations on the repulsive Kane-Mele-Hubbard model at hole doping relative to filling $\nu=1$ electron per unit cell, we find that a Cooper pair formed by a magnon (spin-flip excitation) bound to two holes is stabilized at sufficiently strong interactions and sufficiently large Ising spin-orbit coupling (SOC). This Cooper pair exhibits both finite spin chirality -- signaling a noncoplanar skyrmionic spin texture -- and chiral $f$-wave symmetry. The pairing and spin chirality are set by the Chern number/polarization of the parent Chern ferromagnet. We further find that interactions between skyrmion Cooper pairs evolve from repulsive to attractive as the Ising SOC increases, revealing an intermediate-SOC region where chiral superconductivity can emerge from the condensation of hole-skyrmion Cooper pairs. Our findings provide a novel microscopic mechanism for chiral superconductivity and may be relevant for the recent observation of superconductivity in the MoTe$_2$ moir\'e superlattice.