This paper investigates symmetric carbon tetramer clusters in hexagonal boron nitride (hBN) as potential spin qubits for sensing applications. Using periodic-DFT and quantum chemistry, the electronic, optical, and spin properties of nitrogen-centered (C4N) and boron-centered (C4B) carbon tetramers are predicted. C4N exhibits spin state-dependent optical signals with strain-sensitive intersystem crossing rates, while C4B shows a large intersystem crossing rate and strain dependence. Weak hyperfine coupling to the spin environment results in reduced electron spin resonance linewidths, enhancing sensitivity. The low formation energy of these tetramers makes them promising candidates for high spatial resolution sensing in low-dimensional materials.

Zsolt Benedek, Rohit Babar, Ádám Ganyecz, Tibor Szilvási, Örs Legeza, Gergely Barcza, Viktor Ivády