In Memory of Otto Schärpf, SJ

On 13 June 2019 Prof. Dr. Otto Schärpf, a gifted experimental physicist, universal scholar and priest in the Jesuit Order, passed away at the age of 89. In the community of neutron scatterers he gained international fame as a pioneer of polarization analysis. Since 1991 he was a member of the European Academy of Sciences and Arts.

Obituary Otto Schärpf Obituary Otto Schärpf © SJ-Bild

Obituary Otto Schärpf © SJ-Bild

Otto Schärpf was born in Walldürn in northern Baden in 1929. After grammar school he first turned to philosophical-theological education, which he completed in the Jesuit Order in Pullach (1951-1954) and Innsbruck (1955-1959), and where he was particularly influenced by the teachings of Karl Rahner. After ordination to the priesthood in 1958, Father Otto Schärpf SJ studied physics and mathematics in Munich from 1960 to 1967. He turned his attention to neutrons during his habilitation in 1977 at the Technical University of Braunschweig on the topic “Behaviour of neutrons as they pass through a Bloch wall”. Afterwards, he worked as a lecturer and then as an associate professor for physics at the TU Braunschweig and the Forschungszentrum Karlsruhe before moving to the European Centre for Research with Neutrons, the Institut Laue-Langevin (ILL) in Grenoble, France, in 1979.

Here he was instrumental in advancing the development of polarized neutrons. With extremely modest investments, but an almost superhuman workload, Otto Schärpf realized a completely new instrument for the analysis of cold polarized neutrons. The prerequisite for this was the development of so-called super mirrors: metallic multilayers on glass substrate that reflect cold neutrons of large divergence and only one polarization direction. Otto Schärpf perfected the production of these super mirrors and used them to build so-called Benders as polarizers and polarization analyzers of cold neutrons, the essential elements of his novel neutron scattering instrument. With numerous carefully planned experiments, he then developed the xyz method of polarization analysis, which makes it possible to separate the various contributions to the scattering cross section in a multidetector instrument and thus gain access to correlation functions that can be directly compared with theory. Thus, completely new insights were made available on such diverse issues as the significance of magnetic fluctuations in high-temperature superconductors, the mechanisms of diffusion in condensed matter, near-order in soft matter, magnetic near-order and spin-spin correlations in frustrated magnetic materials, two-dimensional quantum magnets, etc. The results of this research were used to investigate the effects of magnetic fluxes on the magnetic field. Otto Schärpf’s experiences with polarized neutrons and his super-mirror analyzers were also in demand in nuclear physics and were decisive for precision measurements of the beta decay of neutrons.

Otto Schärpf’s work is a good example of how methodological developments can provide completely new insights. They have made polarized neutrons amenable. On the basis of his preparatory work, a large number of neutron scattering instruments at the Heinz Maier-Leibnitz Centre (MLZ) in Garching and at the ILL use polarised neutrons today and make a decisive contribution to making Europe and Germany world leaders in the field of neutron research.

Otto Schärpf was one of the few universal scholars of modern times. He was able to combine his scientific-mathematical work well with his philosophical-theological influence. When his physicist colleagues raised the question of the role of religion, Otto Schärpf told us that for him God stood behind everything, led him to these things and “what he wanted was always easy, even the hardest is easy”. This attitude gave Otto Schärpf an unclouded optimism that was enormously contagious. He was a joyful man who radiated joy in life with his cheerful laughter. And as a theologian he took part in the lives of many of his fellow physicists and accompanied them in important events such as marriages, baptisms and funerals as a priest. After his retirement in Grenoble he increasingly turned again to theology. He returned to Munich and devoted himself to the reappraisal of historical aspects of the Jesuit Order and the philosophical theses of Karl Rahner, in addition to gardening and the maintenance of the Jesuit Order’s computer network.

Joint experimentation with Otto Schärpf was always a great challenge, but also an enormous enrichment. He was the first to play the instrument and remained active until deep into the night, and you had to work hard to keep up with his tempo and workload. An enrichment, since one could learn a lot from him, not only about the experiment, but in the animated dispute of all kinds of scientific, philosophical and theological questions. He never simply accepted the seemingly irrevocable doctrines, but critically questioned everything, whether in experiments, discussions or seminars. Often colleagues became aware that some things that one has accepted as given are not so simple.

With Otto Schärpf, physics loses a brilliant experimenter, a demanding teacher, a critical mind and warmhearted, optimistic person. He was an original, as there are only a few left today, because the scientific system promotes adapted behaviour and punishes “exotics” like Otto Schärpf. Often, however, it is precisely those who do not adhere to the prescribed norms and deviate from the well-trodden path who achieve the truly important breakthroughs. We will keep Otto Schärpf as a brilliant physicist, amiable, active and cheerful person in honourable memory.

Thomas Brückel, Research Centre Jülich, Juelich Centre for Neutron Science JCNS and Peter Gruenberg Institute PGI
Thomas Keller, Max Planck Institute for Solid State Research, Stuttgart
Winfried Petry, Technical University Munich, Physics Department and Research Neutron Source Heinz Maier-Leibnitz (FRM II)
Helmut Schober, Laue Langevin Institute, Grenoble