Klaus von Klitzing Biography

Questions on this topic? Just ask!

World of Biology on Klaus von Klitzing

Klitzing was awarded the 1985 Nobel Prize in physics for his discovery of the quantized Hall effect, Von Klitzing's discovery has had a number of profound effects in both theoretical and practical fields of physics, exhibiting one of the first instances in which quantum effects had been observed on a macroscopic scale. In addition, it made possible the establishment of an entirely new international standard for the ohm, the unit of measure of electrical resistance.

Klaus von Klitzing was born on June 28, 1943, in Schroda, Germany, close to the Polish border, to Bogislav von Klitzing, a forester, and Anny Ulbrich. As World War II turned against Germany, the von Klitzing family decided to stay ahead of the advancing Soviet army and moved westward to the town of Lutten. Three years later, in 1948, they moved again to Oldenburg and finally, in 1951, to the northern town of Essen. Von Klitzing eventually completed his secondary education at the Artland Gymnasium in Quakenbrück.

In 1962, von Klitzing entered the Technical University of Braunschweig, intending to major in physics. He was awarded his baccalaureate degree in 1969 for a dissertation on the electrical properties of indium antimonide, a compound of two semiconducting elements, indium and antimony. Von Klitzing then moved to the University of Würzburg for his doctoral studies, planning to continue his work on semiconductors there. He also accepted a job at the University teaching physics to premedical students. At Würzburg, von Klitzing became particularly interested in the effects of strong magnetic fields on the conducting properties of semiconductors. In 1971, he published his first scientific paper on this topic, "Resonance Structure in the High Field Magnetoresistance of Tellurium," with G. Landwehr, one of his instructors, and was awarded his Ph.D. the following year for this line of research.

A key feature of von Klitzing's ongoing research was the need for stronger and stronger magnetic fields. He spent the 1975 academic year at Oxford University because of the powerful superconducting magnets being manufactured there and, in 1979, continued his research at the High-Field Magnet Laboratory of the Institute Max von Laue-Paul Langevin in Grenoble, France. It was at Grenoble that von Klitzing made the discovery that earned him the Nobel Prize.

The Hall effect (a variation on an electrical phenomenon first observed by the American physicist Edwin Hall in about 1880) is a three-dimensional phenomenon in which an electrical current is passed in one direction through a conducting material while a magnetic field is applied at right angles to the current. The accumulation of electrons along one edge of the conductor results in a potential difference along the face of the material that is called the Hall voltage. The Hall resistance, then, is the Hall voltage divided by the current in the conductor. Under these conditions, von Klitzing observed a totally unexpected effect. As the magnetic field on the sample was strengthened, the Hall resistance also increased as a linear function over a certain range, and then levelled off. Further increases in the magnetic field had no effect on the Hall resistance over another range, but then the Hall resistance began to increase again. After another period, the Hall resistance again levelled off. The final results of the experiment appear graphically as a series of steps. Under conventional experimental conditions, however, the Hall resistance is a continuous, linear function of the imposed magnetic field.

To analyze his contradictory findings, von Klitzing devised an experiment with a number of conditions. Most important was his use of a very thin sheet of silicon that constrained the movement of electrons to two dimensions rather than the three normally allowed. In addition, the experiment was carried out in a powerful magnetic field at temperatures close to absolute zero. In this manner, von Klitzing demonstrated that the Hall effect is quantized; changes in the external magnetic field only induce electrical changes in the silicon in certain steps and not continuously. Von Klitzing found that all the possible quantum steps had a value of a fundamental constant divided by an integer number. That constant, 25,813 ohms, is significant because it is the ratio of two fundamental constants of nature, the square of an electron's electrical charge and Planck's constant. In fact, an effect of this type had been foreseen in 1975 by three Japanese theoretical physicists, T. Ando, Y. Matsumoto, and Y. Uemura. The theory did not predict, however, the high degree of precision that von Klitzing had found.

Von Klitzing's discovery is a significant one for physics. It is one of the few instances in which quantum effects have been observed directly in the laboratory; such effects are normally important only at the level of individual particles such as the electron or atom. In addition, the high precision of von Klitzing's results means that a new and more exact standard for the ohm, the unit of electrical resistance, may be possible.