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Exciton spin dynamics in diluted magnetic semiconductor quantum wells

稀磁半导体量子阱中的激子自旋动力学

基本信息

批准号：
316976768
负责人：
Professor Dr. Vollrath Martin Axt
金额：
--
依托单位：
Lehrstuhl für Theoretische Physik III (Quantentheorie der kondensierten Materie)
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2016
资助国家：
德国
起止时间：
2015-12-31 至 2019-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/316976768?language=en
关键词：
Exciton spin dynamics diluted magnetic

项目摘要

In this project we aim to develop a microscopic, quantum-kinetic theory for the spin dynamics in diluted magnetic semiconductor nanostructures accounting for both, correlations due to the exchange coupling with magnetic dopants as well as the Coulomb interaction, which in particular gives rise to excitonic correlations. The considered technologically important systems are especially promising in terms of innovative applications based on the active use of correlations and quantum coherent dynamical phenomena. This applies in particular to applications in information technology that require a coherent spin control. The basis for future progress in this direction is a deepened understanding of spin dynamics which requires a theory beyond the current state-of-the-art. As a first application of our new theory we shall try to identify quantum kinetic signatures in the spin dynamics of excitonic excitations in quantum wells. These studies will advance the understanding of spin relaxation and should provide insight concerning the role of quantum coherences for spin relaxation. In particular, we shall explore in how far the spin relaxation deviates from an incoherent process that can be modelled by rate equations. In this context we shall also analyze the impact of energetic redistributions between different excitonic states on the spin dynamics.A further focus of the research within this project is the analysis of the interplay between influences of the exchange interaction with magnetic dopants and the spin-orbit coupling of optically excited carriers on the spin dynamics. In diluted magnetic semiconductors usually the exchange interaction dominates. However, varying suitable material parameters in particular in multi-component composite semiconductors allows for tailoring the relative strengths of these interactions in a wide range. Even situations where both couplings are of comparable strength can be realized. Studies of excitations of free carriers in the latter regime give rise to the expectation that also in the case of excitonic excitations a qualitatively new dynamical behavior of the spin system should arise when both couplings are comparable. This could pave the way towards new approaches of spin control.Another target is to explore the possibilities to control the spin dynamics by exciting excitonic states using light with well-defined orbital angular momentum ('twisted light'). This part of the project shall shed light on the question whether the use of novel types of light sources, such as twisted light, that are a focus of topical research opens new ways for the external manipulation of spins that differ from traditional methods as, e. g., the spin orientation via circularly polarized conventional laser light.

在这个项目中，我们的目标是发展一个微观的，量子动力学理论的自旋动力学在稀磁半导体纳米结构占两个，由于与磁性掺杂剂的交换耦合以及库仑相互作用，特别是引起激子相关的相关性。在积极利用相关性和量子相干动力学现象的基础上，所考虑的技术上重要的系统在创新应用方面特别有前途。这特别适用于需要相干自旋控制的信息技术中的应用。在这个方向上的未来进展的基础是自旋动力学，这需要一个超越当前国家的最先进的理论的深入理解。作为我们的新理论的第一个应用程序，我们将尝试确定量子动力学签名的自旋动力学激子激发量子威尔斯。这些研究将推进自旋弛豫的理解，并应提供有关量子相干自旋弛豫的作用的见解。特别是，我们将探讨在多远的自旋弛豫偏离一个不相干的过程，可以模拟的速率方程。在此背景下，我们还将分析不同激子态之间的能量重新分配对自旋动力学的影响。本项目的进一步研究重点是分析与磁性掺杂剂的交换相互作用和光激发载流子的自旋轨道耦合对自旋动力学的影响之间的相互作用。在稀磁半导体中，交换相互作用通常占主导地位。然而，特别是在多组分复合半导体中改变合适的材料参数允许在宽范围内定制这些相互作用的相对强度。甚至可以实现两个耦合具有相当强度的情况。在后一种制度中的自由载流子的激发的研究引起了这样的期望，即在激子激发的情况下，当两种耦合都是可比的时，自旋系统的定性新动力学行为也应该出现。另一个目标是探索通过使用具有明确轨道角动量的光（“扭曲光”）激发激子态来控制自旋动力学的可能性。该项目的这一部分将阐明这样一个问题，即使用新型光源，如扭曲光，这是专题研究的焦点，为不同于传统方法的外部操纵自旋开辟了新的途径，例如。例如，在一个实施例中，通过圆偏振的常规激光进行自旋取向。