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

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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.