Electric field tuning of spin splitting in topological insulator quantum dots doped with a single magnetic ion

Xiaojing Li,Wen Yang,Zhenhua Wu,Liangzhong Lin

doi:10.1038/s41598-019-45067-5

Abstract

We investigate theoretically the electron spin states in a disk-shaped topological insulator quantum dot (TIQD) containing a single magnetic Mn2+ ion. We demonstrate that the energy spectra and the density distributions of the symmetry-protected edge states in a HgTe TIQD can be modulated effectively by a single magnetic impurity Mn2+. Additionally, when an in-plane external electric field is applied., it not only tunes the spin splittings of edge states via the s(p)-d exchange interaction between the electron (hole) and the magnetic Mn2+ ion respectively, but also gives rise to the bright-to-dark transitions in the optical transition spectrum. Such spin properties of TIQDs with single Mn2+ ion as illustrated in this work could offer a new platform for topological electro-optical devices.

Highlights

The topological insulator (TI) is a novel class of quantum matters with insulating bulk characterized by Z2 topological invariant, and metallic edges or surfaces protected by time reversal symmetry (TRS)[1,2,3,4]
In TIs doped with magnetic impurities, one can expect to see the interplay between the spin-orbit interactions (SOIs) and sp-d exchange interaction, which could lead to interesting phenomena, e.g., twisted RKKY interaction[20] and quantum anomalous Hall effect[21]
As an extension of previous studies, in this work, we focus on the spin polarized topological edge states that are modulated by the exchange interactions between a single magnetic dopant and the topological edge states as well as an external in-plane electric field

Summary

Introduction

The topological insulator (TI) is a novel class of quantum matters with insulating bulk characterized by Z2 topological invariant, and metallic edges or surfaces protected by time reversal symmetry (TRS)[1,2,3,4]. It is appealing to systematically address the novel electronic and optical characteristics of a magnetic ions doped TIQDs in the presence of the aforementioned spin polarized topological edge states. As an extension of previous studies, in this work, we focus on the spin polarized topological edge states that are modulated by the exchange interactions between a single magnetic dopant and the topological edge states as well as an external in-plane electric field. The energies of edge states can be effectively tuned by the positions of the single Mn2+ ion and an external in-plane electric fields. The edge states of the TIQD with opposite spin orientation and angular momentum in a such TIQDs exhibit different responses to the doped magnetic ion due to the s(p)-d exchange interactions between the electron (hole) and Mn2+ ion respectively. Our numerical results indicate that transition optical transition rate of edge states in the TIQD varies from bright to dark as the electric field and the position of Mn2+ ion varies

Methods

Discussion

Conclusion