In Memoriam Jean-Pierre Borel (1926 – 2020)

The following obituary was written by former colleagues of Jean-Pierre Borel, SPS honorary member since 2001. It is complemented by some personal memories of Borel’s son Daniel, the founder of Logitech International S.A.

If asked to characterize Jean-Pierre Borel's career and personality in four expressions, we surely would choose pioneering, erudite, modest, and never prejudiced. He was born in 1926 in Neuchâtel. He completed his university studies at the Ecole Polytechnique de l'Université de Lausanne (EPUL) in the newly created physics section under the mentorship of Professor Robert Mercier. In 1954 under his direction, he defended his doctoral thesis entitled "Electrical properties and structures of thin silver films". What attracted him were the very small objects that he was able to create on a substrate depending on the imposed experimental conditions. He realized that it was essential to understand surface properties of matter and he was interested in phenomenological descriptions based on Gibbs' thermodynamic formalism. More than three decades ago, the word nanoscience (or nanophysics) was already used by him to describe this field. Borel realized, that in order to apprehend the crystalline structure of nanoscaled objects, he needed as analytic tool electron microscopy in addition to electron diffraction and besides other experimental methods. He then eventually turned to Eduard Kellenberger, then a young researcher at the University of Geneva. This meeting was not without importance for the future of a young boy of then 12 years old: Jacques Dubochet, the later Nobel laureate.

In 1962, Jean-Pierre Borel held the second chair of physics at the EPUL as "professeur extraordinaire", where he started his teaching activities and founded a research group. Together with Bernard Vittoz, Martin Peter from Geneva and others, they realized that in order to substantially improve the education of doctoral students, the cantonal barriers had to be lowered. The political world followed these pioneering ideas and a postgraduate education system was set up in French-speaking Switzerland and an inter-cantonal agreement signed. JPB lead this new program for the next two years.

In 1968, the EPUL institution was transferred to the Swiss Confederation and became the EPFL. Jean-Pierre Borel was promoted to “professeur ordinaire” with significantly better financial means, and the faculty grew. Thanks to the engagement of EPFL President Maurice Cosandey, a unity of action in both research and teaching was preferred. A physics department was created comprising institutes with several professors. Jean-Pierre Borel, director of the Institute of Experimental Physics and his new colleagues agreed to concentrate their efforts on the study of nanoscale systems for which the contribution of the surface (this invention of the devil according to Wolfgang Pauli that Jean Pierre liked to quote) is decisive: the concept of size effects characterizes the evolution of properties with the size of the system. The so-called “Schwerpunkt" or priority projects were becoming fashionable among decision makers. Jean-Pierre was not happy with such an approach and he liked to recall Jacques Friedel's mischievous comments that there are those who have ideas and seek the means to develop them and those who seek the means and adjust their activity to this end!

Electron microscopy was obviously an indispensable tool. It was important to avoid ego battles since many professors in the School asked for the acquisition of such instruments. Together with Bernard Vittoz and others, they convinced the President of EPFL to concentrate the budget in a "Centre Interdépartemental de Microscopie Electronique" (CIME) of which one of the undersigned was director for several decades bringing it to an international level of recognition; this center still exists.

Jean-Pierre Borel was mainly interested in the size effects that modify thermodynamic, optical, electronic, and magnetic properties (in particular the quantum size effect in conductors predicted by Ryogo Kubo). It is worth mentioning here the fruits of scientific works carried out during the 1970s, which have been widely cited and are still often cited today. With his PhD student Philippe Buffat, he measured the fusion temperature of clusters of gold atoms as a function of size. The experiment was carried out within an electron diffractometer. The authors observed the decrease of the melting temperature by half of the bulk value for cluster sizes down to 2 nanometers! The phenomenological interpretation was based on the fundamental relations of thermodynamics including surface properties.

Among the many facets of Jean-Pierre Borel's endearing personality, we mention his admiration for Ernst Carl Gerlach Stueckelberg von Breidenbach who, in particular, shaped his thinking in thermodynamics and electrodynamics.

At that time, publishing a scientific paper or presenting one's work at a conference in this new research field was not easy. As early as 1976, and in order to create a momentum and establish the field in the scientific community, Jean-Pierre Borel, together with Jacques Friedel (Orsay France), initiated ISSPIC, the International Symposium on Small Particles and Inorganic Clusters. The first symposium took place in Lyon with participants from Europe, USA and Japan, and the second in Lausanne at EPFL four years later. At the end of his speech, Friedel concluded: "small is beautiful, keep small”. This symposium is still being organized with increasing success considering the importance of nanophysics. In 2021 it will take place in Arizona (USA).

Jean-Pierre Borel’s teaching was characterised by a wealth of variations and always governed by his interest and thinking. His teaching of general physics inspired his colleagues and formed for two decades the base at EPFL. There are still many students who benefited from the exactness of his knowledge transfer combined with an optimum of understanding.

Borel dispelled prejudices and he weighted personality and willpower stronger than academic accounting. He, on several occasions, hired a doctoral student whose previous curriculum was not in line with "what would be expected from him". Our Nobel Prize winner Jacques Dubochet benefited from this immense open-mindedness. For many it was not clear, how could an engineer, even a physicist, make a valuable contribution to a molecular biology group without having to repeat all his studies? Jacques Dubochet, in his book, reports that his future thesis director Eduard Kellenberger, who was then professor at the University of Geneva, had listened to Jean-Pierre-Borel.

It is not useless to say also that with the arrival of many colleagues from different backgrounds the "centrifugal forces" were not to be neglected. Moreover, the willingness for "participation" at all levels did not simplify the situation. Jean-Pierre was then one of the major actors at the origin of the important understanding that lead the whole of the young Physics Department to define on the one hand a coherent study plan for the Physics section as well as equally coherent structures for its functioning. In particular, he developed the technical support that guaranteed the originality of experimental research. Meaningful documents were written on his initiative; they have been followed for three decades.

Jean-Pierre was a colleague who always made it clear, within the Institute, that there was no hierarchy; however, his intellectual honesty and clear-sightedness usually set the direction to be taken when all was said and done. He was in charge until 1983, when he decided to hand over his position, not out of weariness but to allow a younger colleague to take over the responsibility. This was one of the fundamental traits of his personality, which enabled him to set up an institute where scientific results went hand in hand with friendship and mutual respect. Jean-Pierre had naturally taken on many responsibilities at the local, national and international level, which he would not like to be highlighted here.

Jean-Pierre Borel had a very fine sense of humor. An expert committee appointed by President Maurice Cosandey included among its members the eminent Victor Weisskopf. To explain our research, Jean-Pierre used models including an icosahedron to illustrate the quinary symmetrical properties when the size of a crystal decreases sufficiently. Victor Weisskopf inadvertently sat on this model, which of course was flattened. Jean Pierre had on his desk this "trophy" on which he had written "icosahedron of Weisskopf".

To conclude, all those who have interacted with Jean-Pierre Borel know that he was a reserved, calm, thoughtful man, but was also capable of enthusiasm and passion. He had great intellectual honesty and was anxious to find in a collegial spirit the balanced and finely tuned solution to a difficult problem. He expressed himself relatively little, but was all the more listened to when he gave his opinion. In spite of his reserved manner, J.-P. Borel has had a real presence and influence among colleagues, collaborators and students. He was able to create unanimity around his actions and his person, which has allowed him to carry out with others what was dear to his heart and seemed important to EPFL.

Jean-Philippe Ansermet, Harald Brune, Philippe Buffat, Jean Buttet, André Chatelain, René Monot, François Reuse