Presentation Information
[8a-E207-1]Real-Time Kerr Rotation and All-Optical NMR Measurements of Nuclear Field Formation in Bulk n-AlGaAs
〇(DC)Andong Shen1, Yusuke Tsujihata1, Reina Kaji1, Satoru Adachi1 (1.Hokkaido Univ.)
Keywords:
Dynamic nuclear polarization,All-optical NMR,n-AlGaAs
In III-V semiconductors, the lattice nuclear spins strongly affect the conduction electron spins through the hyperfine interaction. Under optical pumping in an oblique magnetic field, the polarized nuclei build up an effective field, the nuclear field, reaching a sizable fraction of one tesla. We previously showed that this nuclear field forms in two stages in bulk n-type aluminum gallium arsenide, reflecting two groups of nuclei near and away from the electron localization sites. However, the very fast initial stage and the contributions of individual isotopes could not be resolved by conventional time-resolved Kerr rotation.Here we use two extended methods, real-time Kerr rotation and all-optical nuclear magnetic resonance, measured at about 10 kelvin. In real-time Kerr rotation, the growing nuclear field shifts the electron Larmor frequency, seen as a slow signal oscillation that we convert into the time evolution of the field. A double-exponential fit confirms the two-stage formation, giving a maximum of about 0.58 tesla with fast and slow time constants of roughly ten to thirty seconds and 430 seconds. A residual faster component before the measurement leaves the field already near 70 millitesla at the start, yet the early-stage dynamics are resolved far better than before.In all-optical nuclear magnetic resonance, the modulated pump resonantly depolarizes nuclei when the modulation frequency matches the nuclear precession frequency. Sweeping the field or frequency reveals sharp resonances assigned to arsenic-75, gallium-69, and gallium-71, plus the double-quantum transition of arsenic-75. Every resonance shows an asymmetric sawtooth shape that reverses with scan direction, indicating that nuclear repolarization is slower than the scan rate, consistent with the slow dynamics seen in real time. Together, the two methods give a real-time, isotope-resolved picture of nuclear field formation.