# Engineering Topological quantum dot through planar magnetization in bismuthene

## TL;DR

This paper proposes a topological quantum dot device in bismuthene that uses planar magnetization to control discrete energy levels and spin transport, leveraging quantum confinement of topological edge states.

## Contribution

It introduces a novel topological quantum dot design in bismuthene with tunable energy levels via planar magnetization angles, distinct from conventional quantum dots.

## Key findings

- Discrete energy levels observed through conductance peaks.
- Energy levels and coupling controlled by magnetization and sample size.
- Magnetization angle effectively manipulates quantum confinement and spin transport.

## Abstract

The discovery of quantum spin Hall materials with huge bulk gaps in experiment, such as bismuthene, provides a versatile platform for topological devices. We propose a topological quantum dot (QD) device in bismuthene ribbon in which two planar magnetization areas separate the sample into a QD and two leads. At zero temperature, peaks of differential conductance emerge, demonstrating the discrete energy levels from the confined topological edge states. The key parameters of the QD, the tunneling coupling strength with the leads and the discrete energy levels, can be controlled by the planar magnetization and the sample size. Specially, different from the conventional QD, we find that the angle between two planar magnetization orientations provides an effective way to manipulate the discrete energy levels. Combining the numerical calculation and the theoretical analysis, we identify that such manipulation originates from the unique quantum confinement effect of the topological edge states. Based on such mechanism, we find the spin transport properties of QDs can also be controlled.