Freiburg 2019 – wissenschaftliches Programm

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FM: Fall Meeting

FM 59: Enabling Technologies: Quantum Dots and Superconductivity-based Systems

FM 59.2: Talk

Mittwoch, 25. September 2019, 14:15–14:30, 3043

Metallic magnetic calorimeters for photon sensing with sub-eV energy resolution — Matthäus Krantz, Andreas Fleischmann, Christian Enss, and •Sebastian Kempf — Kirchhoff-Institute for Physics, Heidelberg University, Heidelberg, Germany

Energy-dispersive single photon detection with high quantum efficiency is a key technology for modern quantum science. But despite its great importance, there is a lack of detector concepts providing simultaneously an excellent energy resolution, a quantum efficiency close to 100 %, a fast timing as well as linear detector response.

During the last decade, metallic magnetic calorimeters (MMCs) have proven to fill this gap. MMCs are calorimetric single photon detectors typically operated at temperatures well below 50 mK. They use a paramagnetic temperature sensor strongly coupled to a photon absorber to convert the photon energy into a magnetic flux change that is measured using a current-sensing dc-SQUID via a superconducting flux transformer. The present record energy resolution is 1.6 eV (FWHM) for 6 keV photons. To challenge this limit we have started to develop next-generation MMCs combining temperature sensor and SQUID within a single device to grealty enhance the signal to noise ratio. Our most recent prototype comprises a gradiometric meander-shaped SQUID inductance and planar temperature sensors made of Ag:Er and gives strong reasons to expect that we can achieve sub-eV energy resolution for photon energies up to several keV. We describe the design, microfabrication and optimization of our prototype and discuss the presently achieved performance.