Research Abstract


Control of the spin geometric phase in semiconductor quantum rings

2013年9月26日 Nature Communications 4 : 2526 doi: 10.1038/ncomms3526


長澤 郁弥1, ディエゴ・フラスタグリア2, ヘンリ・サリコスキー2, クラウス・リヒター3 & 新田 淳作1

  1. 東北大学大学院 工学研究科
  2. セビリア大学(スペイン)
  3. レーゲンスブルク大学(ドイツ)
Since the formulation of the geometric phase by Berry, its relevance has been demonstrated in a large variety of physical systems. However, a geometric phase of the most fundamental spin-1/2 system, the electron spin, has not been observed directly and controlled independently from dynamical phases. Here we report experimental evidence on the manipulation of an electron spin through a purely geometric effect in an InGaAs-based quantum ring with Rashba spin-orbit coupling. By applying an in-plane magnetic field, a phase shift of the Aharonov–Casher interference pattern towards the small spin-orbit-coupling regions is observed. A perturbation theory for a one-dimensional Rashba ring under small in-plane fields reveals that the phase shift originates exclusively from the modulation of a pure geometric-phase component of the electron spin beyond the adiabatic limit, independently from dynamical phases. The phase shift is well reproduced by implementing two independent approaches, that is, perturbation theory and non-perturbative transport simulations.