Quantum Defects in 2D Materials for Terahertz Technologies

The emergence of stable terahertz (THz) sources and other THz optical components has spurred the development of many applications. However, THz technologies have thus far not been well integrated into the quantum regime. In this work, we predict that transition metal substitutional defects in two-dimensional transition metal dichalcogenides (TMDs) can serve as quantum defects for terahertz technologies. Central to this prediction is the finding that the zero field splittings between the spin sublevels in these defects are in the sub-terahertz to terahertz range. These zero field splittings are orders of magnitude larger than those found in other common quantum defects, due to the large spin-orbit coupling in these TMD systems. Based on the symmetries of the quantum states as well as first principles calculations of the optical transition energies, we identify defects that can serve as spin qubits, either through resonant excitation or through intersystem crossing channels. Such spin qubits are expected to have a longer spin coherence time compared to spin qubits with smaller zero field splittings. We further propose defects that can potentially be tunable quantum sources of terahertz radiation. Our research broadens the scope for advancements in quantum computing and information science, and lays a foundation for their integration with THz technologies.<br/> <br/><b>Funding Acknowledgement:</b><br/>Supported by the Singapore Ministry of Education under grant number MOE2018-T3-1-005.