26th Australian Institute of Physics Congress and the Australian and New Zealand Conference on Optics and Photonics

From Defects to Devices: First-Principles Design of Atomic Defects in B$_2$SSe for Quantum Technologies

Not scheduled

20m

Belinda Hutchinson Building (The University of Sydney )

Poster AIP | Condensed Matter & Materials (CMM)

Speaker

Ao-Wen Zhou (University of Sydney)

Description

Point defects in low-dimensional semiconductors have emerged as promising building blocks for quantum technologies, including single-photon emitters, spin qubits, quantum sensors, and spin-based quantum devices. Two-dimensional materials are particularly attractive in this context because their atomically thin geometry enables electrostatic tunability, strain engineering, and integration with photonic and electronic devices. However, identifying useful quantum defects remains challenging, since the presence of an in-gap defect level alone is not sufficient. A promising candidate should also exhibit thermodynamic accessibility, stable charge states, deep and localized electronic states, suitable spin multiplicity, and optically addressable transitions.

In this work, we investigate monolayer B$_2$SSe as a candidate host for atomic defects relevant to quantum photonic and spin-based applications. B$_2$SSe is selected because its Janus-type structure breaks out-of-plane mirror symmetry, producing an intrinsic polar environment that may provide additional control over defect electronic levels, spin localization, and optical transitions. Compared with more widely studied centrosymmetric two-dimensional hosts, this structural asymmetry offers an additional degree of freedom for tuning defect properties.

Using first-principles density functional theory, we systematically examine intrinsic and substitutional defects in B$_2$SSe, including vacancies, antisites, and selected impurity-related defects. The key calculated quantities include relaxed defect geometries, defect formation energies, charge-state stability, charge transition levels, localized in-gap states, spin density, and orbital character. For charged defects, finite-size electrostatic effects are treated using established correction strategies for supercell calculations. This study establishes a computational screening framework for identifying promising quantum defects in emerging Janus low-dimensional materials and evaluates the potential of B$_2$SSe as a host platform for future quantum photonic and spintronic devices.