Ferroelectric Theory Meets Experiment in Washington, D.C.

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January 28, 2018

Washington, DC


Yugan Sakthi

SPS Chapter:

The first thing I noticed about the participants as I organized the name tags was the sheer number of countries represented. Universities and research centers from Spain, Israel, the UK, France, Japan, China, India, Australia, the Czech Republic, and much more were represented by some of the foremost physicists, chemists, and materials scientists in the world. I was volunteering at the 2018 Fundamental Physics of Ferroelectrics and Related Materials Workshop, or Ferro2018, and as I sat behind the registration desk handing out name tags and collecting fees, every participant who entered had their own way of saying hello.

Held at the beautiful Carnegie Institution for Science in the heart of Washington, D.C., Ferro2018 was a gathering of the world’s leading researchers in ferroelectric materials. Between the banquet dinners and croissant-laden coffee breaks, I experienced a sharing and developing of knowledge few, if any, undergraduate students get the chance to participate in. My presence there, as such, was as a student, not a researcher, whose goal was to learn as much as possible.

In essence, the study of ferroelectrics involves materials that exhibit ferroelectric behavior—that is, they have a macroscopic non-zero polarization that can be reversed, or switched, with the application of an external electric field. It is a behavior that stems from off-center symmetries of various materials, and the science involved is fundamentally interdisciplinary.

Related topics, all of which (and more) were discussed at the workshop, include multiferroics (which are materials that couple both ferroelectricity and ferromagnetism), relaxors (which display nanodomains of polarization even after the critical temperature is reached), antiferroelectrics (in which neighboring lines of ions are polarized in antiparallel directions), and more. Ferro2018 had experts in all these fields from around the world presenting their research and their findings.

Lasting four days, the workshop was divided into 12 sessions of talks, each covering a specific topic under the umbrella of ferroelectrics, along with a poster session Tuesday night. Following a short reception Sunday evening complete with hors d’oeuvres, in which attendees socialized and discussed their research, the workshop started full-swing Monday morning with the first session of talks, this one on Domains and Domain Walls.

A talk I found especially fascinating occurred in this session, delivered by Dr. Julia A. Mundy of Harvard University and entitled “Functional electronic inversion layers at ferroelectric domain walls.” In a conference where mathematical objectivity was the unspoken lingua franca, Dr. Mundy began her talk with a table of temperature values in Kelvin related to everyday phenomena like “room temperature” or “freezing point of water,” with the intent of providing a more subjective scale by which listeners could contextualize temperatures. By no means did the audience lack experience with these values; rather, it showed that even at levels of research as advanced as this, a human touch to science is always welcome.

The work Mundy and her group have done are pushing the boundaries of ferroelectrics as a field; in this specific part of their research, they sought to answer a central question: how can we explain electronic transport jumps in the ferroelectric ErMnO3? The results produced in pursuit of answers could lead to insight into charged domain walls, which in turn hold great promise as the first truly two-dimensional functional materials. It was a testament to the cutting-edge work displayed throughout Ferro2018.

For emerging researchers like Northwestern University PhD candidate Daniel Hickox-Young, whose research had not yet produced fully presentable results, the poster session gave them an opportunity to present their research, get feedback and ideas, and further discuss any relevant topics. His poster “Evolution of optical phonon modes in doped ferroelectrics” discussed his usage of Density Functional Theory (DFT), a theoretical approach, to investigate lattice properties of a prototypical ferroelectric, BaTiO3. But the poster session was not only for emerging researchers; many who had given talks still presented their current research, and the questions that ensued resulted in deeply engaging conversations.

That structure of talks and posters has been a characteristic element of the workshop since its inception. First hosted in 1989, the workshop has grown over 29 years from a small—yet still international—meeting of theoreticians to a group of over 100 researchers both experimental and theoretical, with some post-doctoral researchers and even PhD. Students scattered in the mix. A few men, namely Dr. Ronald Cohen of the Carnegie Institution for Science and Dr. Raffaele Resta of the University of Trieste in Italy, have been instrumental in the workshop’s organization and development over the years.

Although relatively small in size—compare the 100 attendees at Ferro2018, for example, to the 10,000 at the APS March meetings—the activity and conversations that happen in between talks, during coffee breaks, during the poster session, and after the conference has led to many major breakthroughs in ferroelectrics over the past 30 years.

I sat down with Dr. Cohen and Dr. Resta over dinner at the banquet Monday night, and they provided insight into the workshop’s history, its development, some of those aforementioned breakthroughs, and more. At one point, I asked Dr. Resta, “I heard earlier that the modern theory of polarization was developed at this conference in its early days. What do you know about that?” He replied with a smile on his face. “That was me,” he began, much to me surprise (and awe).

He recounted how in one of the first years the workshop was held, after a fellow attendee had heard his talk, they met to discuss some new ideas, and communicating back-and-forth over the next few months, they developed one of the most fundamental theories of ferroelectrics. That is just one part of Dr. Resta’s CV, which includes some of the first work done on piezoelectric coefficients, which he performed in 1989 using quantum mechanics.

And attending the talks, listening to conversations during breaks and at the poster session, I witnessed glimpses of similar activity all around me. Attendees approached each other after talks, mentioning specifics of their presentations and setting up meetings over lunch or dinner to discuss new ideas and solutions to problems. In that way, Ferro2018 was rightly called a “workshop” and not a “conference”; it was abuzz with intellectual activity. If the cutting-edge research presented was somehow not enough to impress a student like me, the new research it would lead to surely would be.

Wednesday around noon, after the last talks were over and most of the attendees had left, I stuck around to help clean up and catch any last bits of wisdom I could. Dr. Peter Gehring, a researcher at NIST (National Institute of Standards and Technology) and I struck up a conversation. One of the organizers of the workshop, Dr. Gehring had also seen the conference—and the field of ferroelectrics itself—develop over time, and he had a lot to say about it.

Amidst all the research and lunchtime meetings, he had an especially powerful message about the nature of scientific research itself, one he said was crucial to address if ferroelectrics as a field were to progress further. With every new advancement in ferroelectrics, the advancers themselves—the researchers—become more and more specialized, narrowing their spheres of knowledge. “When you only know how to use a hammer, every problem begins to look like a nail,” he said. The best researchers, commented Dr. Gehring, are the ones who can not only perform effective research, but also contextualize that work in the larger field of ferroelectrics—and even physics in general. He said a growing challenge in the future will be to convince scientists to care about the field beyond their own work.

But Dr. Gehring was fundamentally optimistic. “It might seem sleepy at times, but these people here are some of the best around,” he said, speaking to the vast amount of experience and knowledge that had gathered inside those walls for four days.

After the last talks had ended, as the attendees boarded their respective taxis and trains and planes back home, I couldn’t help but think about what Ferro2019 would look like. From the outside, it would most likely be similar; the talks and posters would continue to be filled with equations and diagrams, and the coffee breaks would still serve croissants. But at a deeper level, with new attendees working side-by-side with familiar faces like Dr. Resta and Dr. Cohen, the research shared and knowledge produced would be quite different.


Special thanks to Dr. Ronald Cohen of the Carnegie Institution for Science for his work in organizing Ferro2018 and allowing me the opportunity to attend it, as well as to the SPS for its continued support of physics education and the students who pursue it.