Characteristics of diluted magnetic semiconductor nanostructures

我们研究了量子点中自旋对量子点输运的影响。特别地，详细地研究了由网点自旋引起的许多体效应。我们通过嵌入在Aharonov-Bohm （AB）干涉仪中的量子点（QD）中电子的自旋态进行了干涉实验。我们选择了一个自旋对状态，其环境条件是理想的相似。AB幅值在覆盖对的栅极电压范围内跟踪。两个库仑峰周围振幅的不对称性与量子点中自旋翻转过程与电子的量子失相的理论预测相一致。这些结果构成了由于量子点和干涉仪中自旋纠缠而导致的“部分相干”的证据。在弱耦合状态下，由于法诺效应的影响，出现了法诺-近藤反共振现象。随着耦合强度的增加，两个倾角之间的电导交替减小，呈现出近藤态的增长。从温度依赖性和对磁场的响应来看，我们认为电导降低是由法诺-近藤反共振引起的。在Fano参数为q0的近藤谷，当系统接近与理论预测一致的幺正极限时，观察到相对于栅极电压的相移锁定到Tr/2。在（Ga,A1）As/GaAs异质界面上，通过铁磁半导体（Ga,Mn）As和二维空穴气体之间的界面，在低温输运中观察到巨大的（10000%，在0.07T）磁导率（MC）。MC具有有限的衰减时间，在40mK时几秒内消失，随着磁场的变化迅速恢复。这种特殊的行为可以用库仑隙和无序铁磁性之间的相互作用来解释。通过在界面处引入自组装的InAs量子点，从而使无序的特征长度长得多，从而获得了解释的可靠证据

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