The Beauty of the Laws of Nature
As told by Thomas W. Ebbesen

2014 KAVLI PRIZE IN NANOSCIENCE

MORE ABOUT THOMAS W. EBBESEN

I would not have become a scientist had I not been able to develop my curiosity in the garden of my youth. I spent countless hours playing outdoors, creating imaginary worlds, inspired by everything small and big of the Norwegian wilderness. Starting school at seven felt very confining, compensated only by the gentleness of our teacher. It was soon clear that I was more at ease with numbers than with letters. When my parents gave me my first watch, which was in those days still something very special, I took it apart to understand how it worked. To the credit of my parents, they only reprimanded me lightly but it was years before they gave me another one…

Youth
My parents were hands-on people who rebuilt and fixed their own homes, practical skills that I absorbed by watching them and which have served me all my life both in the lab and in my own home. My preschool years were also marked by the arrival of three siblings that my parents adopted, and suddenly I was the youngest of 6. This made for a lively and loving family environment. Beyond such shared homely activities, my parents were very different, my mother is an artist painter and my father was an officer in the Norwegian Air Force working in military intelligence. He was deeply involved in the U2 surveillance flights over the USSR. When an U2 plane was shot down in 1960 on its way to northern Norway, it had direct consequences for our family. With the political upheaval that followed, it was decided that my father would join the Norwegian military delegation at NATO outside Paris.

So, as I began my third grade, I learned that we were soon moving to France. This would be the first of many moves to different cultures that have marked my life and my work. We arrived in Paris on a cold January day and the adjustment to the new school, learning French and corporal punishment, was extremely difficult. Nevertheless by the autumn, I had joined a regular class where the teacher was kind and inspiring. I had much to catch up as I was placed in 5th grade in view of my age and my size, skipping a year and a half of school learning. In 1967, the military command of NATO moved to Belgium. So by 1968, we were living in Brussels but within 18 months, I returned to Paris with my mother after my parents divorced.

We settled in Montmartre, a charming Parisian neighbourhood, and I attended the Jacques Decours High School where I graduated with a Baccalaureat in physics and math in 1972. Tired of school and not sure what I wanted to pursue, the sciences or the arts, I decided to take a year off and work. I signed up on a Norwegian chemical tanker for some fresh air… It was also a good way to save up funds to attend college in the US. An older American friend, Gene Dye, had told me about undergraduate colleges in the US where one could take courses simultaneously in a variety of subjects, unlike the local universities where specialisation started from day one. The work on the ship was really tough and as a rooky, I was given the most menial jobs, including uninterrupted night watches standing 4 hours on the boat bridge. At the same time it took me around the world, in a time when it was not so easy to visit other continents, to America and Asia through the Panama Canal before returning to Europe via the Indian Ocean. In the spring of 1973, I received letters of admission to several good US undergraduate schools. To their credit, this could not have been based on my low grades but more on my life experience. I chose Oberlin College, Ohio, because its catalogue showed a unique profile at the time, a racially mixed and a very open-minded school. This turned out to be the best choice of my life.

The university years
Oberlin College was a transformative experience. The professors challenged our intellect, provided us with tools to analyze and understand the underlying concepts more than factual knowledge. They were tolerant of our, often youthful, different points of view. The seriousness of our academic pursuits was balanced by much fun and many student-led extra-curricular activities in the arts, theatre, etc. The Oberlin Conservatory provided a constant stream of concerts. I organized a photography cooperative (that still exists) and exhibition for students, had private lessons with an art professor, John Pearson, while at the same time I earned my keep by working as an assistant to the college photographer, Bob Stillwell, washing dishes in the cafeteria and being a dorm counsellor.

I loved physics but feeling inadequate in math, I decided to major in biology all the while taking courses in other subjects. Like all biology majors, I was told that I must take chemistry, a subject I really loathed since high school. When I reached my last year, I was advised that if I took an additional course in physical chemistry, I would be able to 3 have a double major in chemistry and biology. The physical chemistry course was taught by two exceptional teachers: Richard Schoonmaker and Norman Craig. Suddenly chemistry, molecular science, made sense and I decided within a few months that I wanted to become a physical chemist. The conceptual underpinnings of what I learned during that year, I still use today and try in turn to transfer to my own students.

During my first week at Oberlin, I also met Masako Hayashi, a pianist in the Conservatory, with whom I have shared my life ever since. Upon graduation from Oberlin College in 1976, I returned to Paris and enrolled at the Pierre and Marie Curie University for a Master degree. I did odd jobs on the side until the second year when I was lucky and found a lecturer position in biophysics at the medical school of René Descartes University. This enabled me to start a PhD in physical chemistry in the team of my mentors René Bensasson and Michel Rougée. The thesis project was on artificial photosynthesis, an experimental project which introduced me to all the notions of photo-physical chemistry and the chemical kinetics of complex systems.

In 1981, I joined the Notre Dame Radiation Laboratory (Indiana), a DOE facility, as a post-doc. I was told that I did not have to work for anyone so I started immediately my own independent research using the excellent technical facilities available in the institute. Within a year, I published my first paper in Nature, continuing studies of fundamental processes in photo-physical chemistry. Two years later I was promoted to an assistant professor level position. Masako completed her Master degree in piano at the Bloomington School of Music and our daughters Mika and Saya were born.

We spent two years in Japan as I took a leave from the Radiation Laboratory when I received an NSF grant to collaborate with Katsumi Tokumaru, then a professor at Tsukuba University, on artificial photosynthesis. During my second year as a visiting faculty, I was introduced to a scientist from NEC Corporation who was looking for new recruits for their Fundamental Research Laboratory. I had never thought of working in an industrial laboratory but upon visiting their Central Research facility in Tokyo, I was deeply impressed by the dynamic young researchers, and, the outstanding budgets and research facilities. This was the heyday of Japanese corporate research when large profits had been generated by new or improved technology developed within their labs.

The NEC years
After returning to the US, I continued discussions with NEC and in 1988 I joined their labs in Tokyo. With some of my colleagues, we became among the first foreign lifetime employees of a Japanese corporation. This required a challenging adjustment to Japanese culture and the specifics of the NEC corporate environment. We had unlimited means for blue-sky research and we were organized in the Bell Labs style with very small groups, mainly PIs, pursuing each their own topic covering a broad range such as nematode research, quantum chemistry, solid state physics, optics and quantum physics. The cross-fertilisation was very stimulating and I learned much from my colleagues.

In this context, my research took new turns and bloomed. Soon after my arrival, someone passed me the January 1989 issue of Physics Today which contained an article by Serge Haroche (LKB) and Daniel Kleppner (MIT) on cavity quantum electrodynamics. This explained among other things how one could modify the radiative properties of atoms and molecules by placing them in cavities. This notion fascinated me and I believed this would open much potential for molecular science. I asked a microfabrication expert with whom I shared an office if he could make me a sample of small subwavelength cylindrical holes, to act as test-tube nano-cavities (300nm in diameter), in an opaque gold film on a quartz slide, one every micron in a square centimetre. To my surprise when I got the sample I could see through the square cm of holes as if there was nearly no metal. When I recorded a transmission spectrum of the array of holes, it revealed the presence of peaks with a percent transmission that was larger than the area occupied by holes as if even the metal between the holes helped in the transmission process. Most, but not all, the scientists to whom I showed these results were highly sceptical, specially those familiar with optics, since Hans Bethe had demonstrated theoretically in the 1940’s that subwavelength aperture could transmit only a tiny fraction of the light impinging on the hole. Others such as Guido Bugmann and Shunji Kishida encouraged me to pursue this work until I had understood the underlying physics. It would take another 9 years before publication to which I will come back to further down, a period during which I also became very busy with the new world of nanostructured carbons.

The NEC Fundamental Research Laboratory started moving to the Tsukuba site in 1989. Within a year we had the visit of Harry Kroto in the spring who told us about C60, a new form of carbon, and a few months later Krätschmer and Huffman reported a simple way to mass produce it. This was followed by the demonstration of superconductivity in doped C60 at Bell Labs which sparked several NEC scientists into working on these new forms of carbon. Together with Katsumi Tanigaki and others, we set a new world record for molecular superconductivity. Sumio Iijima (2008 Kavli laureate) reported the existence of chiral carbon nanotubes and NEC theoreticians predicted that the chirality would be determining their electronic properties. Pulickel Ajayan and I found a way to mass produce the nanotubes which enabled us and others to measure their actual properties. By 1993, we had started manipulating graphene sheets with Hidefumi Hiura which was the basic material for all the new carbon nanostructures. Soon we were discussing possible use of graphene as electronic material, took a patent and reported this idea in our publications in 1994/95. By then we were ahead of our times… All the while working on nanocarbons, I continued to investigate the transmission of light through tiny holes, eventually with the help of Henri Lezec who joined NEC as a post-doc in another group. A nanofabrication specialist, among other things, he prepared new samples that we then characterized. The fruitful collaboration with Henri would last for several years after he left NEC.

In 1994, I moved to NEC Research Institute in Princeton initially for a two year mission as an expat from NEC Japan to bridge links with the American laboratory. Like its counterpart in Tsukuba, NEC Research Institute also had many outstanding scientists each with their own speciality, fostering much innovative research. There I continued 6 the work on nanocarbon, measuring for instance with Mike Treacy and Murray Gibson the mechanical strength of nanotubes, demonstrating that they were the strongest material known to mankind. When I spoke to Peter Wolff, a senior theoretician, about the “extraordinary” optical transmission through arrays of subwavelength holes, he became fascinated and suggested that it was due to surface plasmons. A week later he came back to my office with a calculation which predicted roughly at which wavelengths the transmission peaks should appear. I was very impressed. He suggested I do more experiments with Tineke Thio, Hadi Ghaemi and Henri Lezec to confirm the model and the phenomenon was finally published in 1998 in Nature. The publication generated considerable interest for the fundamental consequences as well as the technological implications from biomedical sensing to optoelectronics. It also renewed interest for surface plasmon based optics whereby tiny elements and miniature circuits could be sculpted directly in the metal surface using modern nanofabrication tools.

Strasbourg
In 1994 I had also been approached by Jean-Marie Lehn (1987 Nobel laureate in chemistry) to join him in Strasbourg to help him start a new institute called ISIS. After a visit to Strasbourg, Masako and I decided that this would be a propitious place to live and to work. By 1996, I went regularly to Strasbourg to prepare the terrain for our move in 1999 when I became a full time physical chemistry professor. A couple of years later Masako became a professor at the Strasbourg national conservatory. As usual it was a struggle at first to adjust to the new environment. At the same time, it was exciting to participate in the building and running of ISIS with its unique characteristics within French academia. ISIS is pluridisciplinary and mixes in one site people from around the world in both public and private labs. The support provided by the University of Strasbourg and the CNRS has been critical for its success.

In Strasbourg, the work of my team was first mainly focused on surface plasmonic optics, small holes and related structures. We started interacting with European theoreticians such as Francisco Garcia-Vidal, Luis Martin-Moreno and John Pendry (2014 Kavli laureate) and experimentalists such as Sergey Bozhevolnyi, Bill 7 Barnes and Alain Dereux to understand the details of the underlying physics of extraordinary optical transmission and to explore the full potential of surface plasmon optics.

In parallel, I was still curious about the interaction of molecules with their electromagnetic environment and this has gradually taken us into a new direction, most notably in the study of hybrid light-matter states formed by strongly coupling molecules and molecular materials to the vacuum electromagnetic field of a cavity or a surface plasmon resonance. Such dressed states are described with great clarity in the 1989 Physics Today article by Haroche and Kleppner mentioned above. While much focus in the past has been on the quantum or optical properties of the hybrid systems, my interest lies in the way the molecular properties are modified by such strong coupling. For instance we have been able to show that the rate of a chemical reaction and the work function of molecular material can be modified by coupling them to the vacuum field.

At ISIS, I am very lucky to have a small group of dedicated permanent staff: Cyriaque Genet, Eloïse Devaux and James Hutchison who have helped me run the lab over the past 15 years and provided me with stimulating scientific interactions. I have also benefitted from enriching exchanges with my ISIS colleagues, postdocs and PhD students. Above I have mentioned the names of the scientists with whom the interaction was the strongest, nevertheless I have collaborated with many others but citing them all would be beyond the scope of this biography. Our joint publications are a testimony to those collaborations.

My scientific career would not have been the same without Masako who has been a constant source of support and guidance. When I look back, it is clear that I have been enriched by a path that has led me from one culture to another and one research theme to another. When curiosity pushed me into new directions, I was sufficiently ignorant of the subject to reject results that were in contradiction with established truth. To explore the frontiers of knowledge, deep conceptual understanding is necessary but at the same time, one must remain unencumbered by knowledge. Research has thus been a constant learning experience for me and I am forever more in awe at the beauty of the laws of Nature.