Magnetic Ground State of an Individual Fe2+ Ion in Strained Semiconductor Nanostructure

TL;DR

This study demonstrates that applying high strain to an Fe2+ ion in a semiconductor nanostructure can alter its ground state from nonmagnetic to magnetic with a doubly degenerate spin configuration, enabling potential spintronic applications.

Contribution

It shows that strain can fundamentally change the spin state of Fe2+ ions in nanostructures, which was previously considered fixed in bulk materials.

Findings

High strain induces a doubly degenerate ground state with spin projection Sz=+/-2.

Experimental evidence from photoluminescence confirms the magnetic ground state in strained quantum dots.

Strain engineering can enable magnetic properties in otherwise nonmagnetic ions.

Abstract

We investigate spin properties of a Fe2+ dopant, known for having single nondegenerate ground state in bulk host semiconductor. Due to zero magnetic moment such a ground state is of little use for spintronics and solotronics. We show that this well-established picture of Fe2+ spin configuration can be contradicted by subjecting the Fe2+ ion to sufficiently high strain, e.g., resulting from lattice mismatched epitaxial heterostructures. Our analysis reveals that high strain induces qualitative change in the ion energy spectrum and results in doubly degenerate ground state with spin projection Sz=+/-2. An experimental proof of this concept is demonstrated using a new system: an epitaxial quantum dot containing individual Fe2+ ion. Magnetic character of the Fe2+ ground state in a CdSe/ZnSe dot is revealed in photoluminescence experiments by exploiting a coupling between a confined exciton and the single iron impurity.