Low-vibration, helium-free cryostat with 12 T magnet for high-resolution optical measurements

• Subject Area: Condensed Matter Physics
• Term: Funded in 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 558960541

The proposed large research equipment is a “helium-free” cryostat (temperature range 2 K to 350 K) for high-resolution resonance fluorescence spectroscopy and transport measurements in a magnetic field up to 12 Tesla. The device will be used in particular for the investigation of low-dimensional semiconductor heterostructures, which, in various forms, can serve as building blocks for future applications in quantum information technology. One topic of interest is the electrical and optical control of the spin and charge states in these semiconductor devices. Possible candidates are self-assembled quantum dots, which have for many years established themselves as one of the best electrically and optically controllable low-dimensional quantum system. Quantum dots are nanometer-sized semiconductor structures, in which the charge carriers (electrons/holes) are spatially restricted in such a way that quantum phenomena occur. These include energy and charge quantisation as well as exchange interactions and magnetic phenomena, which make quantum dots atom-like model systems. These intriguing physical properties can be investigated by transport measurements and high-resolution resonance fluorescence in such a solid-state model system. In addition, the excellent material quality, which, e.g., leads to Fourier-limited linewidths, leads to a correspondingly high application potential for these quantum systems. In the field of high-resolution spectroscopy (resonant fluorescence), the applicants have carried out pioneering work to understand the Auger recombination, the real-time dynamics of electron tunneling, the electron capture in quantum dots and the internal photoelectric effect. These are physical phenomena that will play a central role in the use of such quantum systems in quantum information processing. This existing expertise in the field of time-resolved transport and high-resolution optical measurements will be further refined in the coming years to investigate novel material systems such as optically active 2D materials (WS2, MoS2, interlayer excitons in WS2/MoS2, etc.) with the proposed large research equipment. The helium-free magnet cryostat will be central to the ongoing work in sub-project A01 of the Collaborative Research Centre 1242 “Non-equilibrium dynamics of condensed matter in the time domain” and in sub-project P4 of the International Research Training Group (IRTG 2803) “Scalable 2D-Materials Architectures (2D-MATURE)”. Other projects for which the large research equipment will be used are the DFG project “Deep-level transient spectroscopy for defect characterization in dielectric materials” and the joint project “Towards universal modeling of quantum measurements” funded by the Mercator Research Center Ruhr, as well as the DFG project “Auger recombination in self-assembled quantum dots”, which is up for extension.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Vibrationsarmer, heliumfreier 12T-Magnetkryostat für hochauflösende optische Messungen
• Instrumentation Group: 0120 Supraleitende Labormagnete
• Applicant Institution: Universität Duisburg-Essen
• Leader: Professor Dr. Axel Lorke