Inelastic spin-photon interactions in spectroscopy of Raman scattering and polarization noise

研究凝聚态物质中的自旋现象是物理学的主要研究方向之一。基于自旋电子学原理的信息处理和数据存储的新方法已经在计算机硬件中实现，并得到了2007年诺贝尔物理学奖的认可。虽然现有的自旋电子学计算机存储器是基于金属多层膜的，但自旋电子学的半导体分支在集成芯片自旋逻辑元件、量子信息单元(量子比特)、用于量子计算和密码学的单光子源方面呈现出巨大的应用潜力。这激发了本项目的主要目标：提供对半导体中自旋-光子相互作用物理的更深层次的洞察，作为光学自旋操纵的基础。在拟议的项目中，为此目的选择的方法是自旋反转拉曼光谱(SFRS)和自旋噪声光谱(SNS)的组合。自20世纪60年代以来，SFRS一直是探测自旋系统的有力工具，而SNS是一个新兴的概念，由于其独特的优点，在大约十年的时间里获得了广泛的关注。理论上已经证明，这两种方法是非常密切相关的，因为它们实际上代表了同一物理现象的两个方面。然而，由于历史的原因，这种深刻的关系从未得到充分的认识，这导致了这两种实验技术及其理论描述的单独发展。因此，一些具有根本重要性的问题仍然没有得到解决，对这个问题仍然缺乏普遍的理解。特别是，这些概念的类比为一种新的相干光学现象的全面理论发展和进一步的实验观测提供了希望，这种现象可以被称为自旋翻转反射。这种新的光学响应应该是混合的，具有SNS信号的一些特征。此外，我们还计划解决另一点，在这一点上，可以深化对SFRS和SNS的普遍看法。这是对局域自旋的顺磁共振和自旋噪声的比较，使用相同的样品进行实验研究，以融合互补的理论描述。作为该项目的一个主要成果，我们期望(I)观察到半导体的一种新的光学响应，以及(Ii)从共同的观点获得对SFRS和SNS现象的实验证实的理解。为了优化团队成员的时间使用，我们列入了次要任务，这些任务将根据德国和俄罗斯分小组之前建立的合作关系，通过对SFRS或SNS的独立研究来解决。也就是说，虽然德国将继续利用SFRS对少数粒子物理进行研究，但俄罗斯将开发新的SNS光谱实验安排。

Studies of spin phenomena in condensed matter form one of the major topical routes in physics. The new approaches to information handling and data storage based on the principles of spintronics are already implemented in the computer hardware and recognized by the Nobel Prize in physics, 2007. While the existing spintronic computer memory is based on metallic multilayers, the semiconductor branch of the spintronics presents a huge application potential in the context of integral on chip spin logical elements, quantum information cells (qubits), single photon sources for quantum computations and cryptography. This motivates the main goal of the present project: to provide a deeper insight into the physics of spin-photon interactions in semiconductors, as a basis for optical spin manipulations. In the proposed project, the method of choice for this purpose is the combination of Spin-Flip Raman Spectroscopy (SFRS) and Spin Noise Spectroscopy (SNS). The SFRS stands since the 1960s as a powerful tool for probing spin systems while the SNS is a rising concept which gained much attention, owing to its specific merits, since about one decade. As has been shown theoretically, both methods are very closely related, as they represent, in fact, two aspects of the same physical phenomenon. However, for historical reasons, this deep relationship has never been fully recognized, which led to a separate development of the two experimental techniques and their theoretical descriptions. As a result, some questions of fundamental importance remained unaddressed and the universal understanding of the problem is still missing. Particularly, the analogy of the concepts holds promise for a full theoretical development and further experimental observation of a new coherent optical phenomenon which can be called spin flip reflection. This new kind of optical response is supposed to be a hybrid, bearing some features of the SNS signal. Moreover, we also plan to address another point where the universal view on SFRS and SNS can be deepened. It is the comparison of the paramagnetic resonance and spin noise of localized spins, being studied experimentally using the same specimens in order to merge the complementary theoretical descriptions. As a major output of the project, we expect (i) the observation of a new kind of optical response of a semiconductor and (ii) gaining an experimentally substantiated understanding of the SFRS and SNS phenomena from a common viewpoint. In order to optimize the time usage by the team members, we include secondary tasks which will be addressed by studies of the SFRS or the SNS independently, in line with the previously established collaboration between the German and Russian subteams. Namely, while studies of the few-particle physics by means of SFRS will be continued in Germany, new experimental arrangements in the SNS spectroscopy will be developed in Russia.