Defects in Oxides for Quantum and Energy Technologies

Abstract: Oxides host a rich variety of electronic, magnetic, optical and catalytic properties, making them indispensable in fields spanning quantum information science, microelectronics and energy conversion and storage. Many of these functionalities originate from localized electronic states, such as those associated with point defects, and their interactions with light and the surrounding oxide lattice. In this talk, I will demonstrate how first-principles calculations can be used to understand, predict and engineer point defects and their excitations in oxides relevant to quantum information science and energy conversion.

I will first discuss Er³⁺-doped CeO₂, a promising spin qubit platform with predicted long spin coherence time and optical transitions in the telecom regime. Our calculations reveal that electron polarons can lead to photoluminescence quenching and charge noise, providing insight into the mechanisms behind experimentally observed optical decoherence.

Next, I will present our search for new spin qubit candidates in MgO, a prototypical oxide used in microelectronics that could enable hybrid quantum technologies. Using high-throughput screening and advanced electronic structure methods, we identified a nitrogen interstitial-magnesium vacancy complex as a favorable spin qubit. I will also discuss recent methodological advances for incorporating spin-orbit coupling into excited-state calculations, enabling the accurate treatment of spin qubits with transition metal and rare earth ions (e.g. Ni²⁺ in MgO and Er³⁺ in CeO₂).

Finally, I will share our efforts to design p-type BiVO₄, a candidate photocathode for solar-to-chemical energy conversion. We found that different acceptor dopants introduce hole polarons with varying degrees of localization and thus have different implications on p-type conductivity. Our joint computational-experimental investigation suggests that Ca²⁺ is likely the most effective acceptor dopant to achieve p-type BiVO₄.

I will conclude with an outlook on how accurate ground- and excited-state electronic structure methods, materials codesign and artificial intelligence/machine learning can be integrated to discover and engineer point defects in oxides. More broadly, I will discuss opportunities to harness the interactions between light, localized charge and the host oxide lattice to enhance the performance and enable new functionalities of oxides in quantum and energy technologies.