بررسي واهلش اسپين-فونون و تابندگي مراكز نقص〖VB〗- در چندگون هاي دوبعدي نيتريد بور

Among two-dimensional semiconductors, boron nitride (BN) with a wide ban‎dgap of 6 eV has shown high potential for hosting solid-state color centers an‎d spin defects. The 2D BN exhibits various polytypes, among which hBN an‎d rBN are more stable than other polytypes. Changes in stacking sequence an‎d their interactions lead to various physical properties. In addition to the desirable properties of hBN, rBN possesses additional properties such as nonlinear optics an‎d ferroelectricity. In 2D materials, due to the reduced phonon density, the spin-phonon relaxation rate is expected to be slower compared to three-dimensional materials; therefore, the use of spin defects in 2D materials is considered an advantage. The spin defect in hBN has attracted considerable attention due to its diverse applications in quantum technologies, including quantum computing, quantum information, an‎d quantum sensing. This spin defect has a spin-1 ground state, an‎d its optical detection of magnetic resonance (ODMR) has recently been demonstrated experimentally. This notable feature enables coherent control of the spin defect at room temperature. Most quantum applications of spin defects depend on the electron spin coherence time, which is significantly limited by spin-phonon interactions. Therefore, determining the coherence time plays a crucial role in the application of spin defects in quantum technologies. In this research, the spin defect in monolayer hBN, as well as stable hBN an‎d rBN structures, were studied using Density Functional Theory (DFT) calculations. After performing phononic an‎d spin calculations, spin-phonon relaxation, which limits the electron spin coherence time, was investigated in the electronic ground state, an‎d the relaxation rates for allowed spin transitions were obtained as a function of temperature. This study demonstrated that the temperature dependence of the relaxation rate is derived from two-phonon Raman processes an‎d second-order spin-phonon interactions. It was also observed that at high temperatures, spin-phonon relaxation is predominantly due to the interaction between the defectʹs electron spin an‎d local phonons arising from the presence of the defect in the lattice. The results indicated that the spin-phonon relaxation time for the defect in monolayer hBN an‎d hBN is comparable, whereas the rBN exhibits a longer relaxation time. In the optical property analysis, it was observed that the reduced symmetry of rBN compared to hBN improves optical properties an‎d increases the radiative lifetime of VB^- in rBN. Consequently, the VB^- in rBN, one of the stable 2D BN polytypes, demonstrates superior spin coherence an‎d optical properties for quantum technology applications compared to hBN.

اسماعيل عبدالحسيني سارسري

مهدي عبدي

پيمان صاحب سرا , احسان عموقربان , سعيد جلالي اسدابادي