After receiving the Abitur in Darmstadt and performing civil service in a hospital, Plefka studied physics at the Technical University of Darmstadt and Texas Agricultural and Mechanical University where he received his Master of Science as a Fulbright Scholar. He received his Doctor of Philosophy from the University of Hannover with a dissertation on supersymmetric Matrix Models in 1995. In 2003 he received the Habilitation at the Humboldt University Berlin.
As a Fulbright Scholar. After postdoctoral work at the City College New York and Nikhef Amsterdam he became a Junior Staff Member at the Albert Einstein Institute, Max Planck Institute for Gravitational Physics in 1998. In 2006 he was awarded a Lichtenberg Professorship of the Volkswagen Foundation in quantum field and string theory at the Institute of Physics at Humboldt University Berlin, becoming Full Professor there in 2011.
In 2014 he held a Visiting Professorship at the Institute for Theoretical Physics at the Eidgenössische Technische Hochschule Zürich.
His research focuses on theoretical high energy and gravitational physics, in particular the AdS/CFT correspondence and hidden symmetries in quantum field theory. His most influential work is the discovery of a hidden Yangian symmetry of scattering amplitudes in North=4 supersymmetric gauge theory together with Drummond and Henn.
He has co-authored a text book on scattering amplitudes in gauge theories which is the first topical book on modern on-shell techniques for scattering amplitudes.
