PUB - Publikationen an der Universität Bielefeld

Correlated defects in 2D materials are promising platforms for quantum technologies, with applications in sensing, photonics, and cryptography. Understanding their response to external perturbations, such as pressure, is crucial for controlling and functionalizing their optical and electronic properties. Although pressure-induced bandgap renormalization is well studied, the mechanisms behind defect-related optical transitions remain unclear, particularly in low-dimensional systems, where dielectric screening and orbital geometry respond to pressure differently than in three-dimensional crystal environments. Here, we show that the large pressure sensitivity up to -22.31 meV/GPa of intradefect transitions in carbon-doped hexagonal boron nitride (hBN:C) is not dictated solely by lattice compression but by a competition between single-particle hopping and many-body Coulomb screening, governed by defect orbital geometry. Out-of-plane orbitals exhibit reduced hopping and Coulomb interactions under hydrostatic pressure due to enhanced screening, whereas in-plane orbitals show increased hopping from enhanced orbital overlap, while Coulomb interactions still decrease. This challenges the view of pressure effects limited to uniform band shift and highlights the dominant role of the defect-related orbital shapes. Our findings establish a predictive framework for pressure-tunable optical transitions in 2D materials, offering a new strategy for identifying and engineering quantum defects.