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，我们的目标是开发一种微观的量子动力学理论，用于稀释磁性半导体纳米结构中的自旋动力学，解释由于与磁性掺杂剂的交换耦合以及库仑相互作用而产生的相关性，特别是引起激子相互作用相关性。所考虑的技术上重要的系统在基于积极使用相关性和量子相干动力学现象的创新应用方面特别有前途。这尤其适用于需要相干自旋控制的信息技术应用。这一方向未来进展的基础是对自旋动力学的加深理解，这需要超越当前最先进的理论。作为我们新理论的首次应用，我们将尝试识别量子阱中激子激发的自旋动力学中的量子动力学特征。这些研究将增进对自旋弛豫的理解，并应提供有关量子相干性在自旋弛豫中的作用的见解。特别是，我们将探讨自旋弛豫与可以通过速率方程建模的非相干过程的偏离程度。在此背景下，我们还将分析不同激子态之间的能量重新分布对自旋动力学的影响。该项目研究的另一个重点是分析与磁性掺杂剂的交换相互作用和自旋轨道的影响之间的相互作用光激发载流子对自旋动力学的耦合。在稀磁性半导体中，交换相互作用通常占主导地位。然而，改变合适的材料参数，特别是在多组分复合半导体中，可以在很宽的范围内调整这些相互作用的相对强度。甚至可以实现两个联轴器具有相当强度的情况。对后一状态中自由载流子激发的研究引起了这样的期望：在激子激发的情况下，当两种耦合具有可比性时，自旋系统也会出现质的新的动力学行为。这可能为自旋控制的新方法铺平道路。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：使用新型光源（例如扭曲光）作为主题研究的焦点，是否为自旋的外部操纵开辟了不同于传统方法的新方法，例如，。例如，通过圆偏振传统激光的自旋取向。