Nano Lett. 22, 4949 (2022)
We present inverted spin-valve devices fabricated from CVD-grown bilayer graphene (BLG) that show more than a doubling in device performance at room temperature compared to state-of-the-art bilayer graphene spin valves. This is made possible by a polydimethylsiloxane droplet-assisted full-dry transfer technique that compensates for previous process drawbacks in device fabrication. Gate dependent Hanle measurements reveal spin lifetimes of up to 5.8 ns and a spin diffusion length of up to 26 μm at room temperature combined with a charge carrier mobility of about 24 000 cm²(Vs)⁻¹ for the best device. Our results demonstrate that CVD-grown BLG shows equally good room temperature spin transport properties as both CVD-grown single-layer graphene and even exfoliated single-layer graphene.

In this German publication we demonstrate how the phyphox BLE library for Arduino can be used to easily visualize data from a custom build sensor on your smartphone. We use CO2 sensor kits as an example, which have been designed as an assembly kit for schools during the pandemic. But besides being a tool to monitor air quality, the easy visualization with phyphox allows for more advanced uses in STEM classes, with experiments in Biology, Chemistry and of course Physics.

Physik in unserer Zeit 53, 151-152 (2022)

As smartphones have become a part of our everyday life, their sensors have successfully been used to allow data acquisition with these readily available devices in a variety of different smartphone-based school experiments. Such experiments most commonly take advantage of the accelerometer and gyroscope. A less frequently used sensor in smartphone-based experiments is the pressure sensor or barometer. Pressure sensors in smartphones can improve indoor navigation, for example in multi-story shopping malls. In a popular smartphone experiment, the barometer is used to determine the current altitude in an elevator with the barometric height formula. Along with accelerometer data and by deriving the height data to calculate the velocity, z(t), v(t), and a(t) plots can be generated and shown to students in real time.

The Physics Teacher 60, 273 (2022) or arXiv: 2201.08064

Walked from the Kronenberg through the Aachenerwald to the Gut Entenpfuhl and played a round of mini-golf there. The weather was more than fine and being outside is always great.

Unter dem Motto 'Faszination Quantencomputer' fand am 14.02.22 der von ML4Q organisierte Quanteen day statt. Hierbei konnten interessierte Schüler:innen in Impulsvorträgen mehr über die Physik hinter Quantencomputern erfahren und anschließend Einblicke in den Alltag von Doktorand:innen bekommen, die in diesem Feld forschen. Von unserem Institut mit dabei waren auch Annika Kurzmann und Corinne Steiner, die bei einer virtuellen Labortour Einblicke in ihre Forschung gegeben haben.

German only – Sebastian Staacks und Christoph Stampfer tragen mit einem Kapitel „Überwachte Rollbewegung mit phyphox“ zu dem neuen Buch „Für alles eine App - Ideen für Physik mit dem Smartphone“ von Thomas Wilhelm und Jochen Kuhn (Springer 2022) bei.

Phys. Rev. Lett. 127, 256802(2021)
We report on finite bias spectroscopy measurements of the two-electron spectrum in a gate defined bilayer graphene (BLG) quantum dot for varying magnetic fields. The spin and valley degree of freedom in BLG give rise to multiplets of six orbital symmetric and ten orbital antisymmetric states. We find that orbital symmetric states are lower in energy and separated by ≈ 0.4–0.8  meV from orbital antisymmetric states. The symmetric multiplet exhibits an additional energy splitting of its six states of ≈ 0.15–0.5  meV due to lattice scale interactions. The experimental observations are supported by theoretical calculations, which allow to determine that intervalley scattering and “current-current” interaction constants are of the same magnitude in BLG.