Spin-orbit quantum impurity and quantization in a topological magnet

TL;DR

This study uses advanced microscopy to reveal how single-atom impurities in a topological magnet induce localized spin-polarized states and quantized orbitals, highlighting strong spin-orbit effects at the quantum level.

Contribution

It demonstrates the first observation of spin-orbit coupled bound states and quantized orbitals induced by nonmagnetic impurities in a topological magnet.

Findings

Impurities create localized spin-down polarized bound states.

Neighboring impurity states interact to form quantized orbitals.

A nonmagnetic impurity can induce spin-orbit coupled magnetic resonance.

Abstract

Quantum states induced by single-atomic impurities are at the frontier of physics and material science. While such states have been reported in high-temperature superconductors and dilute magnetic semiconductors, they are unexplored in topological magnets which can feature spin-orbit tunability. Here we use spin-polarized scanning tunneling microscopy/spectroscopy (STM/S) to study the engineered quantum impurity in a topological magnet Co3Sn2S2. We find that each substituted In impurity introduces a striking localized bound state. Our systematic magnetization-polarized probe reveals that this bound state is spin-down polarized, in lock with a negative orbital magnetization. Moreover, the magnetic bound states of neighboring impurities interact to form quantized orbitals, exhibiting an intriguing spin-orbit splitting, analogous to the splitting of the topological fermion line. Our work collectively demonstrates the strong spin-orbit effect of the single-atomic impurity at the quantum level, suggesting that a nonmagnetic impurity can introduce spin-orbit coupled magnetic resonance in topological magnets.