Paramagnetic point defects in silicon provide qubits that could open up pathways towards silicon-technology based, low-cost, room-temperature (RT) quantum sensing. The silicon dangling bond (db) is a natural candidate, given its sub-nanometer localization and direct involvement in spin-dependent charge-carrier recombination, allowing for electrical spin readout. In crystalline silicon, however, rapid loss of db spin-coherence at RT due to free-electron trapping, strongly limits quantum applications. In this work, by combining density-functional theory and multifrequency (100 MHz-263 GHz) pulsed electrically detected magnetic resonance spectroscopy, we show that upon electron capture, dbs in a hydrogenated amorphous silicon matrix form metastable spin pairs in a well-defined quasi two-dimensional (2D) configuration. Although highly localized, these entangled spin pairs exhibit nearly vanishing intrinsic dipolar and exchange coupling. The formation of this magic-angle-like configuration involves a >0.3 eV energy relaxation of a trapped electron, stabilizing the pair. This extends RT spin coherence times into the microsecond range in silicon required for a future spin-based quantum sensing technology.
@article{arxiv.2402.16523,
title = {Room Temperature Microsecond Coherence of Silicon Dangling Bonds},
author = {J. Möser and H. Popli and T. H. Tennahewa and T. Biktagirov and J. Behrends and W. Akhtar and H. Malissa and C. Boehme and W. G. Schmidt and U. Gerstmann and K. Lips},
journal= {arXiv preprint arXiv:2402.16523},
year = {2024}
}