10:15 〜 10:30
▼ [16a-501-5] Investigating initialization-time dependence of nuclear spin polarization
キーワード：Nuclear spin polarization, Hyperfine Interaction, Oblique Hanle signal
Recently we achieved all electrical spin injection and detection using Co2MnSi/CoFe/n-GaAs system in the non-local geometry. Moreover, we investigated the transient response of the nuclear spins to a change in the magnetic field and a time scale needed for dynamic nuclear polarization (DNP) through the transient oblique Hanle signal (OHS) measurement. Furthermore, we demonstrated a coherent manipulation of nuclear spins using DNP combined with a nuclear magnetic resonance (NMR) technique, which is the first step towards nuclear-spin based quantum bits (qubit). There remain, however, several important issues which must be solved in order to clarify the nuclear spin dynamics. For such a system, a precise control of the nuclear field (Bn) is a critical point to be fulfilled. In this work, we achieve an electrical control of the magnitude and direction of Bn along with a deep understanding of nuclear spin dynamics in GaAs through investigating initialization-time dependence of transient OHSs by both experiments and simulation.
Experimentally, we studied the transient state OHSs at various initialization-time (thold = 25-150 s) which showed two clear side-peaks. Since the side-peak position corresponds to the strength of Bn, the observation of the side-peaks is a direct evidence for nuclear spins to be dynamically polarized by electron spins injected from a Co2MnSi electrode. We also showed that the side-peak positions shifted systematically to the higher magnetic field as increasing thold. This approach presents a precise estimation for the strength of Bn in semiconductors.
Additionally, we simulated those experimental results, (transient OHSs at various thold), taking the rate of polarization due to interaction with polarized electron spins and that of depolarization owing to interaction with lattice into consideration. As a results, a quantitative reproduction is produced, providing a full-description for the behavior of Bn, which will be discussed in the conference.
To sum up, we could experimentally control and estimate the strength of Bn, and analyzed the transient response of the nuclear spins by simulation. These provide a deep understanding of the nuclear spin dynamics in semiconductors.
Experimentally, we studied the transient state OHSs at various initialization-time (thold = 25-150 s) which showed two clear side-peaks. Since the side-peak position corresponds to the strength of Bn, the observation of the side-peaks is a direct evidence for nuclear spins to be dynamically polarized by electron spins injected from a Co2MnSi electrode. We also showed that the side-peak positions shifted systematically to the higher magnetic field as increasing thold. This approach presents a precise estimation for the strength of Bn in semiconductors.
Additionally, we simulated those experimental results, (transient OHSs at various thold), taking the rate of polarization due to interaction with polarized electron spins and that of depolarization owing to interaction with lattice into consideration. As a results, a quantitative reproduction is produced, providing a full-description for the behavior of Bn, which will be discussed in the conference.
To sum up, we could experimentally control and estimate the strength of Bn, and analyzed the transient response of the nuclear spins by simulation. These provide a deep understanding of the nuclear spin dynamics in semiconductors.