Magnetically Defined Qubits on 3D Topological Insulators

TL;DR

This paper investigates how magnetic domain structures on 3D topological insulators can confine surface states into quantum wires and dots, with potential applications in quantum computing due to spin-polarized QAHE states.

Contribution

It introduces a novel magnetic heterostructure geometry for confining topological surface states and identifies QAHE states at quantum dots as promising qubit candidates.

Findings

Confinement occurs at magnetic domain heterostructures.

Quantum dots host highly spin-polarized QAHE states.

The geometry isolates the states from spurious surface modes.

Abstract

We explore potentials that break time-reversal symmetry to confine the surface states of 3D topological insulators into quantum wires and quantum dots. A magnetic domain wall on a ferromagnet insulator cap layer provides interfacial states predicted to show the quantum anomalous Hall effect (QAHE). Here we show that confinement can also occur at magnetic domain heterostructures, with states extended in the inner domain, as well as interfacial QAHE states at the surrounding domain walls. The proposed geometry allows the isolation of the wire and dot from spurious circumventing surface states. For the quantum dots we find that highly spin-polarized quantized QAHE states at the dot edge constitute a promising candidate for quantum computing qubits.