Obituary of Jorgen Lykke Olsen

On March 14, 2006, Jorgen Lykke Olsen, professor emeritus of low temperature physics at the Eidgenoessische Technische Hochschule (ETH) in Zurich, Switzerland, died at his home in Zurich of a cardiac arrest. He was born on May 10, 1923. His father was a Danish civil engineer who had assignments all over the world, and thus the son spent his childhood in Japan and India before he got his final education in England. In the second world war he was drafted into the Royal Navy, and it may have been this experience which led to his love for boats and the sport of sailing. He saw action at sea before he began his study of physics at the University of Oxford. Dr. Kurt Mendelssohn, whom Prof. Frederick Lindemann (later Lord Cherwell) had invited in 1932 to come to Oxford, had pioneered the setting-up of a low temperature laboratory with helium liquefier in the Clarendon Laboratory. He accepted Olsen as his research student, and thus low temperature physics was to become Olsen’s lifetime occupation. His doctoral thesis was on measurement and interpretation of the thermal conductivity of metals down to helium temperatures. In those immediate post-war days at the Clarendon Laboratory, each experimenter not only assisted at the running of the central hydrogen liquefier but also had to liquefy his own helium into his cryostat before the start of each experiment. One can therefore count Jorgen Olsen as one of the pioneers of low temperature physics. It was also at the Clarendon Laboratory that Olsen met his future wife Marianne Bär who was also working in low temperature physics, doing a thesis on the isotope effect in superconductors.

Soon after his doctorate in Oxford, Olsen accepted an offer from the Zurich ETH to install and direct a liquid helium laboratory there. He supervised the installation of a Collins helium liquefier and started a group doing research mostly on superconductors. In those days, superconductivity was still an unexplained phenomenon, and Wolfgang Pauli, among others, urged Olsen to investigate any changes in elastic constants that might occur in the superconducting state. Subsequently, Olsen and his group measured the changes in volume between the two states as well as the thermal expansion in the normal and superconducting states. This was followed by extensive experimental studies of the pressure dependence of the transition temperatures and critical fields of superconductors down to 3He temperatures. He soon started a group to study the effects of Landau quantization, especially oscillatory magnetostriction, in normal metals and alloys. They determined, among other things, the variation of the mean free path of electrons over the fermi surface. In his later years, Olsen started doing his own experiments again, with the help of one laboratory technician. He observed the surfaces waves in superfluid helium which were induced by strong second sound currents.

Olsen published in 1962 a book titled Electron Transport in Metals (Interscience Publishers, New York-London). Based on his lectures to undergraduates at the ETH, it captures in barely a hundred pages a picture as it was known then of the quantum physics of metals whose foundations had been laid by such as Bethe, Bloch, Sommerfeld, Peierls, and Mott. It is written in a style which should give particular pleasure to a reader who is interested in the history of physics, a style that echoes how physics was done then at laboratories like the Clarendon and the Cavendish.

Working in Jorgen Olsen’s laboratory was a privilege in many ways. Not only was communication with him always marked by the legendary politeness of an English gentleman; his collaborators also enjoyed a rare degree of freedom. If a research project didn’t turn out well, it could be changed by the researcher himself. All that mattered were new and interesting results. Once one had such results, Olsen did his utmost to get them published. He sent preprints to his many low temperature friends all over the world. His graduates in this way profited from Olsen’s world-wide personal connections: all of them had good job opportunities, usually through Olsen’s connections.

The character of the Olsen research group was related to their shared extra-curricular interests, which during one period was classic cars such as a 1926 Lancia Lambda, a 1938 BMW cabriolet, and a somewhat younger Riley. The group went out on excursions, usually called “scientific summer schools”, in these cars. Whoever was left behind had the embarrassing job of explaining to the Institute director, if he dropped in, why the laboratory was almost empty.

Olsen’s approach to his research had a special flavour that was much enjoyed by colleagues and friends. Most physicists present their work with an air of confidence which may not be always well-founded. It was different with Olsen. A colleague from his Oxford days recalls how he would begin a talk with an apology for the inadequacy of the results he was about to present. An apology, be it noted, which would turn out to be unjustified. It was all part of a person who, as described by someone who worked with him for more than thirty years, "... was one of the very last gentlemen ( this almost extinct species) ... we lose a good man who, with his humour, tolerance, generosity and intelligence was a very good and dear friend to all of us.”

The union of Marianne Bär who began as physicist and went on to become a noted sculptress and the physicist Jorgen Olsen led to an atmosphere of mutually enriching arts and sciences that prevailed in their home. It became a meeting place for artists, scientists, and musicians who came together to enjoy their gracious hospitality and build bridges between C.P.Snow’s two cultures, as well exemplified in some of Marianne’s artistic creations.

A few years after his retirement, Olsen’s health started deteriorating, to the point that he could no longer enjoy his beloved sailing trips in the Mediterranean. His family, his friends as well as everybody who has ever met him, will miss him. He is survived by his wife Marianne, children Richard and Annette, and grandchildren.