Helium-free cryostat for resonance fluorescence measurements

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The subject of this application is an optical setup for measuring spatially resolved resonance fluorescence at low temperatures (4K – 300K). The instrument is intended to be used in particular for the spectroscopy of low-dimensional solids, such as quantum dots. Quantum dots are nanometer-sized semiconductor structures, which spatially confine charge carriers (electrons/holes), such that quantum phenomena become observable. Among those are (besides energy and charge quantization) exchange interaction and magnetic phenomena, which make quantum dots atom-like model systems. There are fundamental differences, though. For example, quantum dots can be contacted and electrically tuned. Also, external magnetic and electric potentials can compete with the confinement potentials and thus allow for wide quantum tunability. With these properties, quantum dots are not only of fundamental scientific interest. They also form a bridge to present-day , nanometer-size commercial semiconductor structures and offer perspectives as electronic and optical building blocks in future (quantum) information technologies. In this regard, the combination of electronic and optical spectroscopy is of particular interest. The applicant’s group can refer to sizable and relevant previous experience. Here, spatially resolved resonance fluorescence spectroscopy has proven to be a particularly fruitful method. Because of its high spatial and energy resolution, it makes it possible to observe the dynamics of single electrons in a single quantum dot. Examples for such dynamical processes that can be followed optically and with time resolution are: Electron tunneling, Auger recombination, internal photoeffect, and internal electron capture. Furthermore, non-equilibrium states can be prepared and their relaxation into equilibrium can be observed. The proposed instrument will be employed for these and related experiments on quantum dots and other low-dimensional structures. In particular, the setup will significantly strengthen the scientific work in project A01 of the Collaborative Research Centre 1242 “Non-Equilibrium Dynamics of Condensed Matter in the Time Domain". Further scientific work that will benefit from this instrument include DFG project “Auger effects in quantum dots” and a proposal within the Priority Programme 2244 „2D-Materials”.