Imprinting Ground State Chirality on Adatom Spins

TL;DR

This paper introduces a method to detect chiral topological phases by coupling adatom spins to chiral substrates, revealing substrate properties through induced spin chirality.

Contribution

It proposes a novel experimental protocol using adatom spins to identify ground state chirality in doped Chern insulators and chiral superconductors.

Findings

Adatom spins develop noncoplanar order with nonzero chirality due to substrate chirality.

The method distinguishes different substrate types, such as valley-polarized bilayer graphene and $d+id$ superconductors.

Adatom spin chirality encodes the substrate's topological and chiral properties.

Abstract

We propose an alternative experimental protocol for the detection of doped Chern insulators and chiral superconductors. Our approach relies on coupling the target chiral system to adatom spins. Due to the substrate chirality, the adatom spins are expected to order in a noncoplanar configuration with a nonzero spin chirality. Here, we obtain concrete results for chiral substrates which are invariant under arbitrary spin rotations, and are coupled to three adatoms carrying classical moments. By exploring all the accessible magnetic ground states, we identify the regimes in which nonzero spin chirality is induced on the adatom complex. We apply our method to valley-polarized bilayer graphene and $d+id$ superconductors, and find qualitatively different ground state diagrams. Our analysis shows that the adatom spin chirality fully encodes the properties of the substrate chirality.