Professor Dr Klaus von Klitzing

Research Priorities: solid state research, experimental solid state physics, low-dimensional electron systems, quantum Hall effect
Klaus von Klitzing is a German physicist and specialist in experimental solid-state physics. On 5 February 1980, while working at the Grenoble High Magnetic Field Laboratory, he succeeded in discovering and precisely measuring the stepwise change of the Hall voltage under certain conditions. For the discovery of the quantised Hall effect, Klaus von Klitzing received the undivided Nobel Prize in Physics in 1985. With his work, Klaus von Klitzing initiated a new field of research that continues to be highly relevant today.
The quantum Hall effect describes the deflection of electrons in a strong magnetic field at very low temperatures. Under these conditions, a voltage that occurs transversely to an electron current does not grow continuously with the strength of the magnetic field, but in steps. Thus, the resistance also changes in steps. The so-called Hall resistance RH, i.e. the ratio of the Hall voltage to the strength of the current, thereby assumes as plateau values only integer fractions of the von Klitzing constant RK=h/e2 (≈25.8kΩ), where h is the Planck constant and e is the elementary charge. Both are physical constants; the plateau values, therefore, neither depend on the material properties such as the charge carrier density, nor on the sample size, nor on the strength of the magnetic field.
The von Klitzing constant RK is a universal reference for measuring resistance and can be precisely reproduced anywhere in the world. In 1990, it was established by international agreement as the standard for representing the unit measurement ohm. Since the 2019 revision, the International System of Units (SI) has been defined by assigning fixed values to a number of constants, including e and h. As a result, the von Klitzing constant in SI units now has an exact value.
Klaus von Klitzing is a scientist who considers it his obligation to promote interest and enthusiasm for scientific disciplines. He is the eponym and jury member of the Klaus-von-Klitzing-Prize, established in 2005. This award is given to dedicated natural science teachers who help inspire students to work and think scientifically through their outstanding commitment and creativity.