Complete nuclear spin polarization using spontaneous polarization mechanism in semiconductor nanostructures

2018 Fiscal Year Final Research Report

• Project/Area Number: 17K19046
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Research Field: Applied condensed matter physics and related fields
• Research Institution: Hokkaido University
• Principal Investigator: ADACHI SATORU 北海道大学, 工学研究院, 教授 (10221722)
• Research Collaborator: SASAKURA hirotaka
• Project Period (FY): 2017-06-30 – 2019-03-31
• Keywords: 量子ドット / 核スピン分極 / 電子スピン / 核スピンエンジニアリング / スピントロニクス

Outline of Final Research Achievements

In this project, we aimed to establish the methods for optical engineering of nuclear spins, for example control of the polarizability and the polarization direction. Although the clear evidence of spontaneous polarization was not observed, the following experimental achievements were obtained in the exploring processes: a large transverse nuclear spin polarization orthogonal to the injected electron spin can be created. The Hanle curve is anomalously broadened and shows the bistability at the critical field strength. This anomalous Hanle effect is independent of the sign of electron g-factor, and cannot be explained by the standard theory of the optical orientation. We proposed the new model including the nuclear quadrupolar interaction and indicated the qualitative agreement with the observed experimental results.

Free Research Field

半導体光物性

Academic Significance and Societal Importance of the Research Achievements

ナノ構造中の局在キャリア系は超微細相互作用を介して電子と核が強く結合するため，相互に分極を制御できるというポジティブな側面と，互いのデコヒーレンスが伝搬し合うというネガティブな側面が共存する．従って電子-核スピンの結合を十分に理解し，スピン緩和の抑制と分極の制御手法を実現することが重要である．本研究で得た成果により，核四極子相互作用を介した核スピン分極と局在電子スピン制御の道が拓けた．核四極子相互作用は，スピン揺らぎの根源である隣接核スピン間の双極子相互作用を封じるため，その制御により，核スピンバスノイズを低減も期待できる等，半導体物性および量子情報処理分野に重要な知見を与えるものである．