Nuclear spin polarization in silicon carbide at room temperature in the Earth’s magnetic field

Abstract Coupled electron-nuclear spins represent a promising quantum system, where the optically induced electron spin polarization can be dynamically transferred to nuclear spins via the hyperfine interaction. Most experiments on dynamic nuclear polarization (DNP) are performed at cryogenic temperatures and/or in moderate external magnetic fields, the latter approach being very sensitive to the magnetic field orientation. Here, we demonstrate that the 29 Si nuclear spins in SiC can be efficiently polarized at room temperature even in the Earth’s magnetic field. We exploit the asymmetric splitting of the optically detected magnetic resonance (ODMR) lines inherent to half-integer S = 3/2 electron spins, such that the certain transitions involving 29 Si nuclei can be clearly separated and selectively addressed using radiofrequency (RF) fields. As a model system, we use the V3 silicon vacancy (V Si ) in 6H-SiC, which has the zero-filed splitting parameter comparable with the hyperfine interaction constant. Our theoretical model considers DNP under optical excitation in combination with RF driving and agrees very well with the experimental data. We achieve a conversion efficiency of 14% for quadrupole electron spin polarization to nuclear spin polarization, with the theoretical limit at high RF power being 26% under ambient conditions.