Analysis of the transient response of nuclear spins in GaAs with/without nuclear magnetic resonance

Mahmoud Rasly,Zhichao Lin,Masafumi Yamamoto,Tetsuya Uemura

doi:10.1063/1.4943610

Abstract

As an alternative to studying the steady-state responses of nuclear spins in solid state systems, working within a transient-state framework can reveal interesting phenomena. The response of nuclear spins in GaAs to a changing magnetic field was analyzed based on the time evolution of nuclear spin temperature. Simulation results well reproduced our experimental results for the transient oblique Hanle signals observed in an all-electrical spin injection device. The analysis showed that the so called dynamic nuclear polarization can be treated as a cooling tool for the nuclear spins: It works as a provider to exchange spin angular momentum between polarized electron spins and nuclear spins through the hyperfine interaction, leading to an increase in the nuclear polarization. In addition, a time-delay of the nuclear spin temperature with a fast sweep of the external magnetic field produces a possible transient state for the nuclear spin polarization. On the other hand, the nuclear magnetic resonance acts as a heating tool for a nuclear spin system. This causes the nuclear spin temperature to jump to infinity: i.e., the average nuclear spins along with the nuclear field vanish at resonant fields of 75As, 69Ga and 71Ga, showing an interesting step-dip structure in the oblique Hanle signals. These analyses provide a quantitative understanding of nuclear spin dynamics in semiconductors for application in future computation processing.

Highlights

INTRODUCTIONControlling the nuclear spins in a semiconductor through nuclear magnetic resonance (NMR) is one of the promising tools for implementing quantum bits (qubits) for quantum computation applications because they have an extremely longer coherence time than electrons
Controlling the nuclear spins in a semiconductor through nuclear magnetic resonance (NMR) is one of the promising tools for implementing quantum bits for quantum computation applications because they have an extremely longer coherence time than electrons
These analyses provide a quantitative understanding of nuclear spin dynamics in semiconductors for application in future computation processing

Summary

INTRODUCTION

Controlling the nuclear spins in a semiconductor through nuclear magnetic resonance (NMR) is one of the promising tools for implementing quantum bits (qubits) for quantum computation applications because they have an extremely longer coherence time than electrons. The magnetic moment of a nuclear spin is three orders of magnitude smaller than that of an electron spin, so the control of nuclear spins at the nanoscale level is a field of interest.[1] From this point of view, researchers developed dynamic nuclear polarization (DNP) as a way to enhance the NMR signal. Because of these internal interactions, the nuclear spin system reaches the internal thermodynamic equilibrium during a time of order T2 This equilibrium state is defined by a parameter called spin temperature,[25] which may differ strongly from the lattice temperature. The object of this study is to quantitatively address the time dependence of transient nuclear spin temperature along with the steady-state one, based on various possible nuclear spin distributions, to a change in a static magnetic field with and without NMR

SIMULATION MODEL

RESULTS & DISCUSSION

CONCLUSIONS