Karl Heinz Bennemann (born July 31, 1932) is a German condensed matter physicist. He has contributed to the advance on the understanding of traditional BCS and high Tc superconductors, the magnetic properties of alloys, the magnetic properties of low dimensional systems, the physicochemical properties of surfaces, the physicochemical properties of nanostructured materials, ultrafast phenomena, and non-linear optics, among others. His work was recognized through an Alfred P. Sloan fellowship in 1969.
Career Bennemann performed his Diploma and Doctor Rerum Naturalium studies in physics at the University of Münster. The diploma degree was obtained in 1960 under the supervision of Ludwig Tewordt, who was part of the superconductivity group hosted at the University of Illinois at Urbana-Champaign (UIUC). His thesis work was on the theoretical study of the physical effects caused by point defects in copper. In 1962 he obtained the doctoral degree under the combined guidance of Adolf Kratzer and W. Franz. His doctoral work was on the effect of lattice defects on the polarization of the electron gas in solids (thesis titled "Allgemeine Methode zur Bestimmung der durch punktförmige Gitterfehler in Metallen hervorgerufenen Verzerrung des Gitters und Polarisation des Elektronengases"). Through a joint program between the University of Münster and UIUC, he worked fundamental studies on the conductivity in metals, which also earned him the PhD at the latter university, endorsed by James S. Koehler and Frederick Seitz. In the US, Bennemann worked with scientists in a solid-state physics group founded by Seitz in 1959.
Academic career After obtaining his PhD degree, in 1962–1964, Bennemann worked as a postdoctoral scholar in John Bardeen's group, where he studied macroscopic quantum systems with a focus on quantum liquids and superconductivity. He developed a general method to study the electron redistribution around point defects in noble metals and by using the t-matrix method he formulated a theory to calculate the electron distribution in metals. He also contributed to the understanding of the physical properties of point defects in covalent crystals. and extended the pseudo potential theory, introduced by Phillips, to successfully calculate the properties of diamond. In 1964–1965, he was appointed as an assistant researcher at the Institute for Mathematical Physics at the University of Karlsruhe and spent the summer of 1965 working in the Cavendish Laboratory, at the University of Cambridge, England. In Neville Mott's group, he studied the superconductivity in ferromagnetic alloys. Later, he went back to the United States to work in the Institute for the Study of Metals, at the University of Chicago, where he continued with studies of superconductivity in magnetic alloys. Bennemann was especially interested in the role of paramagnetic impurities on the superconducting transition temperature. In 1967, he was appointed as associate professor at the Department of Physics and Astronomy in the University of Rochester, where he received tenure a year later. At that time he contributed to the understanding of the coexistence of superconductivity and magnetic ordering. Furthermore, he proposed an expression for the electron-phonon coupling constant in terms of measurable normal-state quantities and atomic properties, to help explain the superconducting transition temperature in d-band metals. In 1969, while at the University of Rochester, he was awarded an Alfred P. Sloan Foundation fellowship to pursue studies on the magnetic properties of alloys. At the end of 1969, he got offers for a full professorship from several universities: the University of California, Los Angeles, Brown University, Georgetown University, McGill University at Montreal, Canada and the Freie Universität Berlin. He decided to return to Germany and accepted a full professorship at the Institute for Theoretical Physics at the Freie Universität Berlin, in Dahlem, West Berlin. He arrived at a city where some of the most impactful physics was developed before the Second World War and which had suffered large devastation during the world conflict. The Freie Universität Berlin was founded in 1948, under especially difficult circumstances, in the American Sector of the divided city subjected to the Russian blockade. At that time the Friedrich-Wilhelms-Universität, where Albert Einstein, Erwin Schrödinger, Max Planck, Werner Heisenberg and others had developed their seminal work, was split into the Humboldt Universität located in the east sector and the Freie Universität in the west. Today's Institute for Theoretical Physics, was founded at the beginning of the 1970s when the university was reorganized and underwent extensive expansion. It took more than 20 years to fully organize the university and provide the infrastructure. Bennemann contributed to the creation of an international physics institute of excellence. In the decades that followed, he ran projects on many important problems in condensed matter physics. With the collaboration of international scientists and graduate students he contributed to the scientific environment at the Freie Universität, and the development of science in other countries, including Argentina, Brazil and Mexico.
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