Harald P. W. Ibach (born 15 April 1941 in Rheine)[1] is a German solid state physicist.
Ibach received his doctorate in 1969 from RWTH Aachen University with his dissertation Thermische Ausdehnung von Silizium und Zinkoxid (Thermal expansion of silicon and zinc oxide) and habilitated there in 1972 with his habilitation thesis: Low energy electron spectroscopy — a tool for studies of surface vibrations.
From 1975 he was a docent and then a professor ordinarius at RWTH Aachen University, as well as director of the Institut für Schichten und Grenzflächen (Institute for Layers and Interfaces), and chair for Experimental Physics IV A in Jülich.
He is the co-author, with Hans Lüth [de], of a German standard textbook on solid state physics.
[2] He also wrote, with Douglas L. Mills, a standard reference on electron energy loss spectroscopy.