Resonant optical spectroscopy and coherent control of Cr4+ spin ensembles in SiC and GaN

TL;DR

This paper demonstrates optical spin polarization and magnetic resonance of Cr4+ impurities in SiC and GaN, showing their potential for quantum information applications due to narrow linewidths and strong zero-phonon emission.

Contribution

It reports the first optical control and detection of Cr4+ spin states in SiC and GaN, highlighting their suitability for quantum technologies.

Findings

Achieved ensemble optical spin polarization and ODMR of Cr4+ in SiC and GaN.

Resolved individual spin sublevels at low magnetic fields.

Over 73% of optical emission is within the zero-phonon lines.

Abstract

Spins bound to point defects are increasingly viewed as an important resource for solid-state implementations of quantum information technologies. In particular, there is a growing interest in the identification of new classes of defect spin that can be controlled optically. Here we demonstrate ensemble optical spin polarization and optically detected magnetic resonance (ODMR) of the S = 1 electronic ground state of chromium (Cr4+) impurities in silicon carbide (SiC) and gallium nitride (GaN). Spin polarization is made possible by the narrow optical linewidths of these ensembles (< 8.5 GHz), which are similar in magnitude to the ground state zero-field spin splitting energies of the ions at liquid helium temperatures. We therefore are able to optically resolve individual spin sublevels within the ensembles at low magnetic fields using resonant excitation from a cavity-stabilized, narrow-linewidth laser. Additionally, these near-infrared emitters possess exceptionally weak phonon sidebands, ensuring that > 73% of the overall optical emission is contained with the defects zero-phonon lines. These characteristics make this semiconductor-based, transition metal impurity system a promising target for further study in the ongoing effort to integrate optically active quantum states within common optoelectronic materials.