Numerical study of dephasing in disordered electron systems

在这个项目中，我们研究了无序电子系统中的数值退相和量子输运中的相关问题，在无序电子系统中，复量子干涉起着重要的作用。这种干扰在低维系统中尤其重要，例如二维电子系统(2DES)。由于耦合到外部自由度(如热浴)而导致的干涉分解是退相的根源。将附加铅(S)耦合到储集层(S)是在数值计算中考虑退相的一种方法。因此，在本项目中，我们研究了以下几个方面：1)研究三端几何结构中的电子输运：为了考虑退相，需要研究具有两个以上端子的系统。我们已经开发了一个程序来研究这个问题，并计算了输运系数。作为副产品，我们分析了存在自旋-轨道相互作用时自旋极化电流的产生。(文件2和4)2…进一步研究自旋在量子输运现象中的作用：研究了自旋自由度在量子输运中的作用。特别令人感兴趣的是低维系统中具有很强的自旋轨道散射的系统。我们模拟了电导涨落(文献10)、2DES中的Anderson相变(文献8和15)以及二维以下的Anderson相变(文献1)。在2DES中，通过假设一个含时的势，研究了存在自旋-轨道散射时的退相(文献14)。3)随机相模型的研究：为了研究相在量子输运中的重要性，我们研究了随机相模型(文献6和11)。4)量子网络模型的研究：研究了研究量子输运现象的简化模型--网络模型(文献5)。5)研究了量子霍尔效应中的边态：我们知道量子霍尔边态具有超长的退相时间。我们已经详细地研究了无序存在时的这些态(文献3和7)。较少

In this project, we have studied numerically dephasing and related topics in quantum transport in disordered electron systems where complex quantum interference plays an important role. The interference is especially important in low dimensional systems such as the 2 dimensional electron system (2DES). The breakdown of the interference due to the coupling to external degrees of freedom such as a heat bath is the origin of dephasing. Attaching extra lead(s) coupled to reservoir(s) is a way to take into account the dephasing in numerical calculations. In this project, therefore, we have studied the following :1) Study of electron transport in the 3 terminal geometry : to take into account the dephasing, study of systems with more than two terminals is needed. We have developed a program to study this issue, and have calculated the transport coefficients. As a byproduct, we have analyzed the generation of spin polarized current in the presence of spin-orbit interaction. (Papers 2 and 4.)2 … More ) Study of the role of spin in quantum transport phenomena : the role of the spin degree of freedom in quantum transport has been studied. Of particular interest is the system with strong spin-orbit scattering in low dimensional systems. We have simulated conductance fluctuations (paper 10), the Anderson transition in 2DES (papers 8 and 15) and the Anderson transition below 2 dimensions (paper 1). Dephasing in the presence of spin-orbit scattering has been studied in the 2DES by assuming a time-dependent potential (paper 14).3) Study of random phase model : to investigate the importance of phase in quantum transport, we have studied the random phase model (papers 6 and 11).4) Study of quantum network model : the network model that is a simplified model to study the quantum transport phenomena has been studied (paper 5). Since the model is simple, we are able to attach many leads to a sample.5) Study of edge states in the quantum Hall effect : the quantum Hall edge states are know to have extraordinary long dephasing time. We have studied these states in the presence of disorder in detail (papers 3 and 7). Less