Von Klitzing, Klaus

views updated Jun 08 2018

Klaus von Klitzing

The Von Klitzing constant, which looks like this: RK = h / e2 = 25812.807449(86)Ω, was named in honor of Klaus Von Klitzing's (born 1943) discovery of the Quantum Hall Effect. The constant has been listed on the National Institute of Standards and Technology Reference on Constants, Units, and Uncertainty. In his constant, Von Klitzing gave the inverse value of one quantum of electrical conductance. It was an important step in the development of the science of physics, for it opened the door to allow a more precise measurement of the ohm, the standard unit of electrical resistance.

Early Study of Physics

Von Klitzing was born on June 28, 1943, in Schroda, Germany, near the Polish border. He was born to Bogislav von Klitzing and Anny Ulbrich. Because of World War II, which was in full force at the time of his birth, von Klitzing's family was relocated several times when he was very young. As the tide of the war changed from Germany's side to that of the the Allies, the von Klitzings were forced to move again in order to stay ahead of the Soviet army, which was advancing across Germany to claim victory for the Allied Nations.

The von Klitzings ended up in the town of Lutten for a short while. In 1948 they moved again, this time to the town of Oldenburg. Their last move was in 1951, when they moved to Essen in the north. Von Klitzing attended high school at the Artland Gymnasium in Quakenbruck in Lower Saxony, near Essen.

In 1962, after he had finished his high school studies, von Klitzing decided to go on to university, so he enrolled at the Technical University at Braunschweig. He had always been good at science, especially physics, so it was his intention to get a degree in that field. He graduated with a bachelor's degree in 1969, having written his graduate paper on the "Lifetime Measurements on InSb," which concentrated on the electrical properties of indium antimonide. The substance was a compound of two semi-conducting elements: indium and antimony.

Worked and Researched at University of Wurzburg

After graduation von Klitzing was accepted to the University of Wurzburg, where he studied under Dr. G. Landwehr. While he was there he also took a job teaching physics to premedical undergraduate students. He knew he wanted to continue his work on semi-conductors, so he took classes and discussed the issue with his mentor, Landwehr. In his research he became enthralled by the effects of strong magnetic fields on semi-conductors. It was a field of study that had always held a fascination for him. His first paper on the subject was published in 1971. It was about "Resonance Structure in the High Field Magnetoresistance of Tellurium," and was co-written with Landwehr. He earned a Ph.D. in 1972, having done his research and work on the "Galvanomagnetic Properties of Tellurium in Strong Magnetic Fields."

Von Klitzing went on to do post-graduate work at the university. His research, however, began to require stronger and stronger magnetic fields, which could only be created with large and very expensive equipment: something not all research facilities could afford to provide. For this reason he had to leave the university to pursue his studies. He did some research work at the Clarendon Laboratory at Oxford University from 1975–76. He went to Oxford University for the powerful superconducting magnets that were being made there. After he was finished with his work at Oxford he returned to Wurzburg. There he continued any work he could do at the university, and in 1978 he worked on and completed his "habilitation," a type of certification needed to gain a professorship in Germany.

Studied the Hall Effect

He had continued his research in Wurzburg, but now needed an even stronger magnetic field in which to do his work. He went to the High Magnetic Field Laboratory at the Institute Max von Laue-Paul Langevin in Grenoble, France, from 1979–80. While there he discovered the quantum values in the Hall effect, and found the Von Klitzing constant, RK = h / e2 = 25812.807449(86)Ω. A group of scientists from Japan, Tsuneya Ando, Yukio Matsumoto, and Yasutada Uemura, had theorized the quantum effect as early as 1975, but the first person to get experimental research results proving it was von Klitzing. The three Japanese men did not, however, guess at how precise the constant would be.

When he came up with his constant von Klitzing was working on a discovery that physicist Edwin Hall made more than a century before von Klitzing did his work. Hall had discovered that a transverse volt is created across a conducting or semi-conducting material when a magnetic field is applied to that material at a right angle and an electrical current is flowing through it. It was named the Hall effect. The Hall effect is done on three-dimensional objects and involves passing an electrical current one way through a material that can conduct electricity while a magnetic field has been applied to the current at a right angle. The Hall effect, according to the Dictionary.com website, "is a phenomenon that occurs when an electric current moving through a conductor is exposed to an external magnetic field applied at a right angle, in which an electric potential develops in the conductor at a right angle to both the direction of current and the magnetic field."

Von Klitzing was doing his research and discovered that as the magnetic field grew stronger, the Hall resistance also grew stronger for a while and then evened out. After its leveling stage no increase in magnetism had any effect on the Hall resistance for a time, then it would increase again, then level off, then increase, and so on. When it was graphed, the measurements looked like a flight of stairs, ever increasing upwards. This was not what the Hall effect had said would happen. Normally the Hall resistance was a continual line, with no steps of leveling off or stagnation. Von Klitzing set out to discover why this leveling off had occurred.

Discovered the von Klitzing Constant

First he set up his experiment to conform to extremely precise ingredients. He used an extremely thin sheet of silicon to make the test two dimensional rather than the usual three. Then he made the temperature extremely cold, almost to absolute zero. Only then did he apply the magnetic field. He got the same results again, only this time he discovered something else. What he discovered was that the steps in the graph were all of a certain, never-changing value. The constant was 25,813 ohms. It was an important number because it happened to be exactly the ratio of the electron's electrical charge squared compared to Planck's constant.

Von Klitzing tried the test again, taking the Hall effect to extremes, focusing on two-dimensional objects that were kept at a temperature near absolute zero. Again, when these were exposed to extraordinarily strong magnets he discovered that the Hall effect was not continual, but only occurred in discrete steps with a finely tuned precision. It was an important discovery in the study of electrical currents. The von Klitzing constant soon became the standard unit used to describe electrical resistance. The constant has since been listed on the National Institute of Standards and Technology Reference on Constants, Units, and Uncertainty, which is where all the universally excepted theories and formulas are written. Von Klitzing in his constant gave the inverse value of one quantum of electrical conductance. According to the Royal Swedish Academy of Sciences his discovery opened up a new research area that has become very significant and important since its discovery. Research and Development magazine said, "By making it possible to probe the conductivity of electronic components very precisely, the discovery has allowed physicists to make standardized specifications for a wide variety of materials."

His discovery was also very important in the field of physics. It is one of the only times that quantum effects, usually guessed at on very small scales such as that of electrons and atoms, were seen in a laboratory. It also meant that it was possible that one day a more precise value for the ohm, the standard unit of electrical resistance, could be found.

Won the Nobel Prize

In 1980 von Klitzing left the University of Wurzburg to take a position as professor with the Technical University in Munich, Germany. While he was there he garnered many awards for his research on the Hall effect. He was awarded the Walter-Schottley Prize of the German Physical Society in 1981, and the Hewlett Packard Prize of the European Physical Society in 1982. He stayed at the University of Munich until December of 1984. In 1985 he went on to become the director of the Max Planck Institute for Solid State Research in Stuttgart. The change in job titles was advantageous and allowed him unfettered access to the sorts of equipment he needed to continue his experiments with magnetic fields.

In 1982 some researchers at Bell Labs in New York discovered that the von Klitzing constant worked not only for integers, which is what he tested, but also for fractions of the quantum Hall effect. These were equally important discoveries, but could not have been found had it not been for von Klitzing's original research. This research brought von Klitzing back into the public eye, and so for his earlier discovery von Klitzing was awarded the Nobel Prize in 1985. It was a rather late but welcome acknowledgement of von Klitzing's work.

On a personal note, Von Klitzing married Renate Falkenberg in 1971. The couple had two sons and one daughter. As of the beginning of 2007 von Klitzing was still director of the Max Planck Institute for Solid State Research in Stuttgart. He has continued his work on low dimensional electronic systems that are kept at low temperatures and afflicted with high magnetic fields.