Characteristics of diluted magnetic semiconductor nanostructures

稀磁半导体纳米结构的特性

• 批准号: 14076208
• 负责人: KATSUMOTO Shingo
• 金额: $ 27.71万
• 依托单位: The University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research on Priority Areas
• 财政年份: 2002
• 资助国家: 日本
• 起止时间: 2002 至 2005
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-14076208/
• 关键词: spin electronics; diluted magnetic semiconductors; tunneling effect; mesoscopic systems; quatum dots; Fano効果; 近藤効果; 量子コヒーレンス; 巨大トンネル磁気抵抗; クーロンギャップ; 磁気ポーラロン; 干渉効果; 電子波位相; 強磁性半導体; 巨大磁気抵抗; ハーフメタル; 2重障壁トンネルダイオード; スピン偏極正孔

We have studied the effect of spins in quantum dots on the transport through them. Especially, many body effects caused by the dot spins are studied in detail.We performed experiments on the interference through spin states of electrons in a quantum dot (QD) embedded in an Aharonov-Bohm (AB) interferometer. We have picked up a spin-pair state, for which the environmental conditions are ideally similar. The AB amplitude is traced in a range of the gate voltage that covers the pair. The behavior of the asymmetry in the amplitude around the two Coulomb peaks agrees with the theoretical prediction that relates a spin-flip process in a QD to the quantum dephasing of electrons. These results constitute evidence of "partial coherence" due to an entanglement of spins in the QD and the interferometer.We observed the Fano-Kondo anti-resonance in a quantum wire with a side-coupled quantum dot In a weak coupling regime, dips due to the Fano effect appeared. As the coupling strentgh increased, cond … More uctance in the regions between the dips decreased alternately, showing the growth of the Kondo state. From the temperature dependence and the response to the magnetic field, we conclude that Ihe conductance reduction is due to the Fano-Kondo anti-resonance. At a Kondo valley with the Fano parameter q 0, the phase shift locking to Tr/2 against the gate voltage is observed when the system is close to the unitary limit in agreement with theoretical predictions.We observed huge (10000% at 0.07T) magnetoconductance (MC) in low temperature transport through an interface between a ferromagnetic semiconductor (Ga,Mn)As and a two-dimensional hole gas at a (Ga,A1)As/GaAs hetero-interface. The MC has a finite decay time and vanishes in a few seconds at 40mK while it rapidly recovers with a variation of magnetic field. The peculiar behavior is explained by the interplay between the Coulomb gap and disordered ferromagnetism. Sound evidence of the interpretation is obtained by introducing self-assembled InAs quantum dots at the interface, thus making the characteristic length of the disorder much longer Less

我们研究了量子点中自旋对量子点输运的影响。特别是，我们详细研究了点自旋引起的许多体效应。我们对嵌入Aharonov-Bohm(AB)干涉仪中的量子点(QD)中电子的自旋态干涉进行了实验。我们已经获得了一种自旋对状态，其环境条件非常相似。AB幅度在覆盖该对的栅极电压范围内跟踪。两个库仑峰附近振幅的不对称性与理论预言一致，即量子点中的自旋翻转过程与电子的量子退相有关。这些结果构成了由于量子点和干涉仪中自旋的纠缠而产生的“部分相干”的证据。我们观察到在弱耦合状态下，具有侧耦合量子点的量子线中出现了Fano-Kondo反共振，出现了由于Fano效应而产生的凹陷。随着耦合强度的增加，条件…凹陷之间区域的更多亮度交替下降，显示出近藤状态的增长。从对温度的依赖关系和对磁场的响应，我们得出结论：电导降低是由于Fano-Kondo反共振所致。在Fano参数为Q0的近藤谷，当系统接近理论预测的么正极限时，观察到Tr/2的相移锁定。在(Ga，Al)As/GaAs异质界面处，我们观察到铁磁性半导体(Ga，Mn)As与二维空穴气体之间的界面存在巨大的(0.07T时为10000%)磁导(MC)输运。MC有一个有限的衰减时间，在40mK时在几秒钟内消失，而随着磁场的变化，MC迅速恢复。库仑带隙和无序铁磁性之间的相互作用解释了这一特殊行为。通过在界面引入自组装的InAs量子点，从而使无序的特征长度变得更短，从而获得了解释的声音证据

项目成果

Direct observation of a neutral Mn acceptor in Gai.Mn.As by resonant x-ray emission spectroscopy

通过共振 X 射线发射光谱直接观察 Gai.Mn.As 中的中性 Mn 受体

• 发表时间: 2005
• 期刊: Phys. Rev. B 71
• 作者: Y.Ishiwata;T.Takeuchi;R.Eguchi;M.Watanabe;Y.Harada;K.Kanai;A.Chainani;M.Taguchi;S.Shin;M.C.Debnath;I.Souma;Y.Oka;T.Hayashi;Y.Hashimoto;S.Katsumoto;Y.lye
• 通讯作者: Y.lye

超伝導・超流動

超导/超流动性

• 发表时间: 2006
• 作者: 勝本信吾;河野公俊
• 通讯作者: 河野公俊

K.Kobayashi, H.Aikawa, S.Katsumoto, Y.Iye: "Mesoscopic Fano Effect through a Quantum Dot in an Aharonov-Bohm Ring"Physica E. (in press).

K.Kobayashi、H.Aikawa、S.Katsumoto、Y.Iye：“Aharonov-Bohm 环中量子点的介观 Fano 效应”Physica E.（出版中）。

S.Katsumoto, K.Kobayashi, H.Aikawa, A.Sano, Y.Iye: "Quantum coherence in quantum dot - Aharonov-Bohm ring hybrid systems"Superlattices and Microstructures. (in press).

S.Katsumoto、K.Kobayashi、H.Aikawa、A.Sano、Y.Iye：“量子点中的量子相干性 - Aharonov-Bohm 环混合系统”超晶格和微结构。

Observation of the Fano-Kondo antiresonance in a quantum wire with a side-coupled quantum dot.

• DOI: 10.1103/physrevlett.95.066801
• 发表时间: 2004-10
• 期刊: Physical review letters
• 影响因子: 8.6
• 作者: Masahiro Sato;H. Aikawa;K. Kobayashi;S. Katsumoto;Y. Iye