Phase Transitions, Materials and Applications

Research Group of Prof. A. Schilling

 

Research and teaching

We are interested in selected topics in materials research, spanning the entire spectrum from searching new materials, their characterization and corresponding applications. We have been particularly active in superconductivity, magnetism and thermodynamics.

At present we are working, for example, on superconducting thin-film nanowire single-photon detectors working in the X-ray range. We could show that these detectors (called X-SNSPD’s) nicely work with X-rays, notably with negligible dark-count rates (see, e.g., AIP Advances 6 (2016) 115104, IEEE Trans. Appl. Supercond., Vol 23 (2013) 2200505).

We are also focusing on the thin-film physics of amorphous superconductors such as WSi, where we are exploring the magnetic phase diagram. We have, for example, identified a field-driven transition from a Bose insulator to Fermi insulator at low temperatures (Phys. Rev. B 97 (2018), 214524).

We have recently completed a long lasting investigation on the spin-dimer system Ba3-xSrxCr2O8, which is believed to host a magnetic Bose Einstein condensate (BEC) at low temperatures and high magnetic fields (New J. Phys. 18 (2016) 033001, Phys. Rev. B 96 (2017) 184201, Phys. Rev. B 98 (2018) 144115). These studies were accompanied by theoretical work on the effect of anisotropy (New. J. Phys. 19 (2017) 113002) and the magnetic Grüneisen parameter (Phys. Rev. B 98 (2018) 144416).

The ac-response in the peak-effect region of type-II superconductors has also been studied within two PhD projects, explaining, for example, the mystery of the double peaks in the ac-susceptibility of Nb3Sn (Physica C 492 (2013) 133) and demonstrating that the peak effect in the resistivity can be switched on and off by the application of a small external ac magnetic field (Phys. Rev. B 81 (2010) 094510).

A very nice device developed in our laboratory is the equivalent to a thermal inductor. We initially used it to create oscillatory thermal currents, in analogy to ac-currents in electric LC circuits. Using this type of thermal inductor it is possible to measure heat capacities with very high accuracy by measuring the resonance frequency of the thermal current (Rev. Sci. Instrum. 82 (2011) 094901). Using the same device, we could recently show that we can build a setup in which heat is flowing from cold to hot without any external energy input, in apparent contradiction to thermodynamics (Science Advances 5 (2019) eaat9953). With this device, it might be possible one day to cool large quantities of hot materials well below room temperature without the need for an external energy source. We finally showed that this counter-intuitive process is still in full accordance with the second law of thermodynamics.

A complete list of our publications can be found here.

Professor Andreas Schilling is regularly teaching physics lectures for students of Physics and other natural sciences. He always tries to motivate the students with unconventional examples, for instance, with mysteries on Newton’s cradle and the third Newton’s law "actio = reactio", or more advanced brain-teasers on the equivalence principle, or the entanglement of photons. These puzzles, a complete list of his lectures and other interesting things and can be found on our teaching website.

last modified: 2. Mai 2019 - sts