First principles theory of the nitrogen interstitial in hBN: a plausible model for the blue emitter

Abstract

Color centers in hexagonal boron nitride (hBN) have attracted considerable attention due to their remarkable optical properties enabling robust room temperature photonics and quantum optics applications in the visible spectral range. On the other hand, identification of the microscopic origin of color centers in hBN has turned out to be a great challenge that hinders in-depth theoretical characterization, on-demand fabrication, and development of integrated photonic devices. This is also true for the blue emitter, which is an irradiation damage in hBN emitting at 436 nm wavelengths with desirable properties. Here, we propose the negatively charged nitrogen split interstitial defect in hBN as a plausible microscopic model for the blue emitter. To this end, we carry out a comprehensive first principles theoretical study of the nitrogen interstitial. We carefully analyze the accuracy of first principles methods and show that the commonly used HSE hybrid exchange-correlation functional fails to describe the electronic structure of this defect. Using the generalized Koopman's theorem, we fine tune the functional and obtain a zero-phonon photoluminescence (ZPL) energy in the blue spectral range. We show that the defect exhibits high emission rate in the ZPL line and features a characteristic phonon side band that resembles the blue emitter's spectrum. Furthermore, we study the electric field dependence of the ZPL and numerically show that the defect exhibits a quadratic Stark shift for perpendicular to plane electric fields, making the emitter insensitive to electric field fluctuations in first order. Our work emphasize the need for assessing the accuracy of common first principles methods in hBN and exemplifies a workaround methodology. Furthermore, our work is a step towards understanding the structure of the blue emitter and utilizing it in photonics applications.

33 pages, 10 figures, 3 tables

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Cited by in corpus (8)

• Quantum Optics Applications of Hexagonal Boron Nitride Defects
• Blue quantum emitter in hexagonal boron nitride and carbon chain tetramer: proposition of identification
• Electrically pumped h-BN single-photon emission in van der Waals heterostructure
• Creation and Microscopic Origins of Single-Photon Emitters in Transition Metal Dichalcogenides and Hexagonal Boron Nitride
• First-principles computational methods for quantum defects in two-dimensional materials: A perspective
• An atlas of photonic and plasmonic materials for cathodoluminescence microscopy
• Deterministic generation of single B centers in hBN by one-to-one conversion from UV centers
• Single photon emitters in hBN: Limitations of atomic resolution imaging and potential sources of error