Interview | FVB, PDI | 26-08-2022

“We want to light up the whole house”

Professor Roman Engel-Herbert took the position of Director of the Paul-Drude-Institut in July 2021. In the interview, he talks about his plans.

Prof. Dr. Roman Engel-Herbert | Photo: Ralf Günther

Professor Roman Engel-Herbert studied physics in Jena, Germany, completed his PhD at PDI and worked as a postdoc in Canada and the USA. His last position there was researching at Pennsylvania State University, where he held a professorship in the Department of Materials Science and Engineering since 2010. He returned to Germany in July 2021 to take up the position of Director of PDI and Professor of Experimental Physics / Materials Sciences at Humboldt-Universität zu Berlin. His research focuses on the synthesis of novel materials using molecular beam epitaxy. He takes over from PDI Director Prof. Henning Riechert, who directed the Institute until his retirement in 2019.

Mr. Engel-Herbert, how was your start as the new director of PDI?

It was a good start, if a bit rushed. I’d have liked to have had everything nicely tied up in the US first by the end of the calendar year 2021, before starting at PDI. But given the long appointment negotiations, which are unfortunately common in Germany and seem to be unavoidable, further delays would have been hard to justify. The fact that people were accepting virtual meetings as a new norm were very helpful to me and worked in our favor. We even introduced new formats of virtual communication at PDI, one being the online tool Gathertown. There, we created virtual rooms for PDI where we can host our events – such as the annual meeting with the Scientific Advisory Board and the PhD Student Seminar. We launched a virtual colloquium, hosted on Zoom, which makes it much easier now for external people all over the world to participate in the scientific discourse held at PDI. All this helped us very much. Something new may seem insurmountable at first but, if you give it a try, you might just discover: it actually works!

What is the strategy you are pursuing for PDI?

We are looking to make ourselves strong in novel materials at PDI, without neglecting our core competencies. The last 30 years were focused on semiconductor materials. And we’ve driven these classical material systems to near perfection – to the point where it’s almost getting “boring.” Around ten years ago we saw the paradigm shift towards “More than Moore,” in other words functional diversification beyond the conventional semiconductors. A flood of new material systems washed over us. These are all highly promising, but so far they haven’t reached the level of perfection needed to make them useable in their respective applications – not even by a long stretch. Our mission is to position PDI such that we can play to our strengths: the growth of thin films by molecular beam epitaxy, atomic level control of complex nanostructures, the development of new synthesis approaches to enable working with these novel materials having additional functionalities, combining and integrating them with one another. There is new physics to be discovered and there are new technologies to be developed. We have to take a broader stance and need to courageously forge ahead, because it is still unclear what the “right” material of future technologies might be. We do experiments at PDI and our motto is: Just try it out – nothing ventured, nothing gained.

We want to remain and become leaders in five material classes: The classical Group V arsenides and nitrides, in other words the “established” semiconductors; we want to strengthen the oxides that we have already been working with very successfully as binary oxides within GraFOx, and additionally extend our research into ternary oxides with a perovskite structure. We want to research the material classes of chalcogenides and van der Waals materials as well as Heusler alloys. The ladder material class already has a long history at PDI in the context of spintronics, and among them many candidate materials with topologically protected, conductive surface states are suspected.

PDI primarily does basic research. What’s it like to be a pioneer?

It is exciting, fascinating, demanding and sometimes seemingly futile at first, but in retrospect very fulfilling. I would like to explain this in more detail using an example. In the past people were developing semiconductors as light sources, so-called light emitting diodes or LEDs. In these materials, the band gap plays an important role because it determines the wavelength emitted and therefore the color. After achieving red and green LEDs everyone was moving towards semiconductor materials with larger and larger band gaps. Blue and white were the cool things, and semiconductors with bigger band gaps were needed to realize this. The community started working on basically two materials: the majority on zinc selenite, a few on gallium nitride. It seemed clear at the time which material would win: zinc selenite, because it initially worked so much better. Back then PDI said: No, our core expertise is in fundamental research, and we’re going to look at why the nitrides don’t work. And who won the race in the end? The Nobel prize for the invention of efficient blue LEDs went to scientists who had focused on the nitrides. At PDI, we did and contributed many important results in this field, while others pushed towards maturation of this technology. And what is the result? We can go to a hardware store and pick up an LED lamp for three bucks fifty that needs only one seventh the energy previously required by an ordinary light bulb invented by Edison, and that has a 20 times longer lifetime. That is the entire arc of the story, and I am sure that some of the pioneers, who by the way are still working at PDI to this day, have a little smile of pride on their faces whenever they see LED Christmas tree lights. Sometimes we forget that one of the key breakthroughs at the beginning of this example was the growth of nitrides, the basic research that solved the fundamental problems. For me, this raises two questions that need to be addressed: How do we make sure that we communicate this and other pioneering achievements of PDI more clearly? How do we prepare ourselves at PDI to follow this arc a little longer, and bring in our core expertise also to help accelerate materials maturation at higher technology readiness levels?

You want to focus more on the application aspect – as part of the new strategy?

Yes, on the one hand, we want to open ourselves up to new materials and, on the other hand, we want to raise the technology readiness level (TRL). TRLs indicate how far a technology has evolved distinguishing nine levels. At level 1, nothing is clear yet; it’s where you keep pursuing something in order to learn and understand more. Level 8/9 is where you can just go to the hardware store and pick the product off the shelf. PDI does fundamental research, this is where we have our strengths – we can’t be expected to develop new technologies to the maturity of a finished product.  But we can certainly take them to a higher TRL. We have a great cleanroom, excellent growth capabilities and the know-how to use it, which is complemented by expertise in structural analysis and spectroscopic characterization. We can better foster the implementation of patents and coordinate collaborations with partners in industry, research groups and institutes. PDI is well positioned to serve the lower TRLs. For example, a recently defended PhD thesis work contained research and development efforts that ranged from TRL 1 to 4. A new material system has been tested: the device – a spin valve – has been characterized, and we can now exactly assess what and how much the material has to offer, and what would be a possible application area. This was all achieved in four years thanks to the complementary expertise of different people at PDI. That is why we have to incorporate the application aspect early into the discovery process. We have to change our culture a little bit and ask ourselves: We have gotten something new, so what are we going to do with it?

You say you want to change the culture. Does that apply to other areas as well?

Yes, another aspect of our strategy is to become more diverse – not in terms of research, but in terms of PDI employees. For example, we want people on our team who have grown up in different countries and under different circumstances, and who have had different experiences, because then they will have completely different associations when encountering an unknown problem. To illustrate this point with an analogy: If you are in a dark house and you want to turn on the lights in all rooms, some might try to reach for the wall switch. That works – but not necessarily for all rooms. A different room might be lit by floor lamps or by a light with a pull cord dangling in the middle of the room. This means that if any one person were to tackle the problem on their own, they would only turn on specific lights in the house, only certain rooms – not all rooms – will be lit, but nevertheless we would feel accomplished. We sometimes forget that we are quickly intoxicated by our success; I mean, at least the lights are on in some rooms, right? We tend not to realize that our strategies have failed us in other rooms. That is why we have to become more diverse – because we want to light up the whole house, quickly and efficiently.

PDI is a part of the Forschungsverbund Berlin. What does that mean for you and your institute?

The Forschungsverbund Berlin gives me a sense of security. There are people here who understand our needs very well and who support us through many difficult processes, such as the legal handling of recruitments, for example.

What I also like is that because FVB is so diverse with its different institutes, we can all learn from each other. For example, when it comes to equal opportunities we are lagging behind in the field of physics – in basic research – compared to the life and environmental sciences. Within FVB, we have the chance to look a bit into the future and to ask them questions: How did you get there? What does one have to look out for? That helps me. So the advantage is not only that a joint administration can be effective – and by that I don’t just mean cost effective – rather, it provides access to a wider range of possible solutions. That’s an inherent strength of FVB.

And there is a generational change coming up. FVB has been around for 30 years now. Many of the people who helped me at PDI when I was a PhD student are still here, but will soon be retiring. This poses the challenge of making sure that we don’t lose too much that they have been building up so nicely, but on the other hand, it presents an opportunity to break new ground. This is true for the institutes as well as for the Joint Administration. We can take a chance and venture in a new direction without neglecting our strengths. That is one of the reasons why I came here.

This Verbundjournal issue focuses on career paths in science. What would you like to pass on to the new generation of scientists?

It is important to be clear about your goals. You can be bold in your choices. It’s important to have a healthy understanding of risk, courage for the gaps – and to stop thinking you have to do things perfectly. I think that this generally applies and not just to our young scientists. It’s completely normal to make mistakes. When they occur, we catch them, we endure them as a team. Understanding and progress come from analyzing both our successes and our failures. Mistakes play a big part in the process of gaining knowledge. It’s drawing conclusions and learning from them that counts – this is where the team and people with more experience can help. If you try to avoid mistakes, you don’t move forward – you just keep coming back to that same place where you know how not to make mistakes.

Researchers should always work in the proximity of the knowledge horizon and constantly venture beyond it – they need to keep moving forward, endure and cope with the fact that not everything works. In doing so, it is important to motivate yourself with what is going well. Research is not comfortable, so our core values are all the more important, they strengthen and unite us: a good culture of error, healthy self awareness and reflection, and teamwork. PDI actively strives to help shape the framework at FVB so that these values are firmly rooted in our FVB community.

The interview was conducted by Anja Wirsing.

Translation: Peter Gregg