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，我们详细研究了量子点自旋引起的各种体效应，并在Aharonov-Bohm（AB）干涉仪中进行了量子点中电子自旋态干涉的实验研究。我们得到了一种自旋对状态，其环境条件在理想情况下是相似的。在覆盖该对的栅极电压范围内跟踪AB幅度。在两个库仑峰周围的振幅的不对称性的行为与理论预测一致，该理论预测将量子点中的自旋翻转过程与电子的量子退相联系起来。这些结果构成了量子点和干涉仪中自旋纠缠所导致的“部分相干”的证据。我们在带有侧耦合量子点的量子线中观察到Fano-Kondo反共振。随着耦合强度的增加， ...更多信息 在两个凹陷之间的区域中，电导率交替下降，显示了近藤态的生长。从温度依赖性和对磁场的响应，我们得出结论，Ihe电导降低是由于Fano-Kondo反共振。在Fano参数为q 0的Kondo谷，当系统接近幺正极限时，观察到了与门电压相关的Tr/2相移锁定，与理论预测一致（10000%在0.07T）的低温输运中通过铁磁半导体（Ga，Mn）As和二维空穴气之间的界面的磁导（MC），A1）As/GaAs异质界面。MC有一个有限的衰减时间，在40 mK时几秒钟内消失，而随着磁场的变化，它迅速恢复。这种奇特的行为可以用库仑能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InAs量子点，从而使无序的特征长度更长，可以获得解释的合理证据。

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