Quantum Defects in 2D Transition Metal Dichalcogenides for Terahertz Technologies

Substitutional transition metal (TM) point defects have recently been controllably introduced in two-dimensional (2D) transition metal dichalcogenides. We identify quantum defect candidates through a first-principles materials discovery approach with 25 TM elements substituting Mo and W in 2D MoS₂ and WSe₂, respectively. We elucidate trends in the charge transition levels for these 50 systems and report the existence of defects with spin-triplet ground states and a zero-field splitting (ZFS) in the terahertz (THz) regime, in contrast to typical gigahertz values. These defects can couple to resonant near-infrared radiation, providing a route to applications as high-fidelity qubits controlled by spin-dependent optical transitions. The THz ZFS implies that these high-fidelity operations can take place at higher temperatures compared to the case for GHz qubits. Our results also point toward the possibility of realizing a single-photon THz emitter. This work broadens the scope of quantum defects, highlighting the opportunities for next-generation THz quantum technologies─an area of growing interest given the rapid advancement in the development of THz sources and detectors.