This post is an excerpt from the formally non-public part of my DFG Heisenberg grant final report (about half of the actually interesting part). I hope it will help people do better. Some personal information has been redacted.
The backstory
In 2018, when I first submitted a Heisenberg program proposal, funding was declined. One referee report was full of misinformation and misinterpretations, the other criticized the methods in one of the suggested research subtopics. Overall this sufficiently lowered the ranking of the entire submission. Anyway, as the saying goes, stand up again, brush down coat, re-adjust crown, keep going. The proposal was updated, the doubtful part replaced, a response to the misinformation added, and of course also some more exciting research ideas included.
At that point I decided to go for full risk. While the DFG Emmy Noether program deliberately funds a junior research group consisting of a PI and PhD students or a post-doc, the DFG Heisenberg program is more adjusted along the customs of humanities and funds the PI alone. It is still supposed to provide a base for independent research at the level of associate professor though, which is why one can concurrently submit a supporting research grant proposal for equipment and personnel. The advantage of doing so is that this can form a coherent overall funding package, the disadvantage is that a negative review of any part of the package will drag it down in its entirety, see above.
Complementing the overarching Heisenberg proposal for my own position and its research, I submitted in 2019 two additional research proposals ("Einzelanträge"). One focused on the continuation of the Emmy Noether project, tuning optomechanics of single-wall carbon nanotubes towards strong coupling and coherent control, and including such nice ideas as, e.g., coupling mechanics with coherent states in double quantum dots. This was a highly complex project, intended for two PhD students (and the two students were really required because of the combination of multi-step fabrication and complicated experiment). In addition, it was adjusted to fit to the topic of a Graduate Research School (GRK) proposal under preparation back then in Regensburg. The idea of the second grant was to try out something new, and establish quantum transport measurements on MoS2 nanotubes – a material where already a lot of optical measurements existed but the transport physics of quantum dots was so far completely unexplored. Here, one PhD student was requested; furthermore the topic was deliberately chosen to be in the area of interest of a new Regensburg Collaborative Research Centre (SFB), SFB 1277, in the hope of further financial support options.
Because of the significant amount of university-bound equipment acquired from SFB funds, and the potential difficulties of moving “my” large dilution refrigerator, I chose again Universität Regensburg as host institution.
In the meantime, my employment contract in Regensburg ran out (thanks Wissenschaftszeitvertragsgesetz), so I went to the Low Temperature Laboratory, Department of Applied Physics, Aalto University, Finland for one year as full-time employed visiting professor; my thanks go to Prof. Pertti Hakonen for making this possible. Two weeks later COVID broke out, but Aalto was a great place to be both scientifically and to sit out the pandemic. And in autumn a sequence of excellent news followed; the Heisenberg grant was approved, and in addition the Emmy Noether work on microwave optomechanics was awarded the Walter Schottky Prize 2021 of the German Physical Society. So, things were clearly brightening up, or so I thought.
A more detailed inspection of the grant approval letter provided a somewhat more mixed image. One referee explicitly and clearly supported the request for two PhD students in the optomechanics project, the other also explicitly lauded all details, including the excellent funding plan, of the optomechanics project, but additionally stated that the impact of the MoS2 nanotube project would be larger (this was likely written before the announcement of the Walter Schottky Prize). As result, only one PhD position for optomechanics was granted by the funding committee. Hope always dies last, but in retrospect I can now confirm my immediate suspicion that this reduction of funding killed the optomechanics project from the start. My initial “plan B” for additional optomechanics funds was not available anymore, since the Regensburg Graduate Research School had in the meantime made an ultrafast turn towards other research topics. Further, even though this project was the direct continuation of the Walter Schottky Prize work, it turned out to be extremely difficult to find and hire a PhD student for it. The project started on 16 March 2021, and only on 1 August 2022 a PhD student arrived.
In comparison, the MoS2 nanotube project start-up went much more smooth, and [...] started work on his PhD straight on the 16 March 2021. All hope of a financially significant participation in the Regensburg SFB 1277 was however shattered already by a brief conversation with the back then SFB speaker, who made clear that nothing beyond appointing me “associated member” would even be considered. Well, you can't allow “junior scientists” to become too successful…
Scientific progress
I had attempted to keep the optomechanics project going in Regensburg during my time in Finland via a remotely-supervised MSc student, who successfully optimized coplanar waveguide resonator geometries and produced and tested the corresponding devices. When I came back, I quickly found another MSc student who was very enthusiastic to start with optomechanics experiments. However, we also quickly found out that the nanotube growth oven had broken in the meantime, requiring the whole process to be optimized from the start, and the MSc project literally became a year of getting carbon nanotube growth going again from zero. Now in 2026 (!) the quality of nanotubes transferred into a circuit is finally showing excellent results again. That said, the nanotube optomechanics project had many delicate parts, from nanotube growth and transfer to coplanar resonator chip design and fabrication, and no number of MSc students recruited into my group could really replace the missing second PhD student.
[...] On the MoS2 nanotube side, progress was slow but steady, and the PhD student did excellent work. Making contacts to MoS2 nanotubes turned out to be even more complex than contacts to carbon nanotubes or a 2D MoS2 monolayer. A technical breakthrough in the latter system by researchers from MIT and TSMC, among others, provided a path forward, and indeed their approach also led to occasional good results with the MoS2 nanotubes. Obtaining these good results reproducibly, however, was again another complex optimization step; we solved that in 2025 and subsequently managed first physically interesting low-temperature measurements.
In general, across both subprojects, work was slowed down very much by continuous equipment break-downs and oddities in the Regensburg cleanroom. "The SEM for e-beam writing is down" turned out to be one highly regular e-mail subject (for any possible value of "the SEM"). Mystery changes in resist properties, micrometer-scale shifts in the written structures, interruptions in the air conditioning that led to water condensation in the whole cleanroom, ... The department bought a Heidelberg Instruments mask-less aligner (a laser writer for lithography), which was nice but of limited usefulness – since for nanophysics you actually need nano-resolution! Plus there were some other annoying events; e.g., during the installation of a new dilution refrigerator next door someone opened up our (then evacuated) 3He/4He circuit in the pump room to air, which we only noticed when we tried to cool down and suddenly were pumping air into the cold dilution refrigerator insert. Luckily, nearly no isotope mixture was lost.
Experimental work took significantly longer than expected, but eventually did yield interesting results right at the end. As stated above, for the research details of the two subprojects, I refer to the final reports of the research grants [...] and [...].
[...]
Early career stage researchers
I am proud to be able to say that during my ~16 years in Regensburg I have supervised 7 PhD students and 27 MSc or Diplom students. During the Heisenberg period specifically, two PhD students should be named, [...] and [...]. [...] is currently helping a new professor in Regensburg build up his lab on a post-doc position and considering remaining in academia (which he would definitely be suited for). [...] is still busy measuring beautiful data and writing up his dissertation, while being paid by SFB1277.
At the end of the official project runtime (and my employment) in March three MSc students were still active; two have graduated by now, the third one recently handed in his thesis.
