Hinweis: Aufgrund von geplanten Wartungsarbeiten wird die Website am Mittwoch, 30. April 2025, ab 15:00 Uhr nicht erreichbar sein.
Wir bitten dadurch entstandene Unannehmlichkeiten zu entschuldigen und danken für das Verständnis.
To path indicator Subpages of “Newsdetail“ To navigation by target groups To navigation by topic To quick access To footer with other services
To content
Panoramic view on the North Campus © Jürgen Huhn​/​TU Dortmund
Prof. Klaus von Klitzing Speaks at TU Dortmund University

From the Nobel Prize in Physics to the New Kilogram

-
in
  • Top News
  • People
Prof. Dr. Klaus von Klitzing in the Audimax. The TU logo in the background. © Roland Baege​/​TU Dortmund
In the packed Mail Lecture Hall, Prof. Klaus von Klitzing told the audience about the discovery of the Quantum Hall Effect and the significance of his research.
In 1985, Prof. Klaus von Klitzing received the Nobel Prize in Physics for the discovery of the Quantum Hall Effect. On 21 January, he discussed the significance of his discovery for physics and the new definition of the kilogram in 2019 in the Main Lecture Hall at TU Dortmund University. His entertaining and well-attended lecture was part of the “Initial Spark” lecture series, the title of which refers to Alfred Nobel’s experiments at the nearby Dorstfeld mine.

On 5 February 1980, at 2 a.m., von Klitzing made his groundbreaking discovery. While analyzing the flow of an electric current through a semiconductor at the High Magnetic Field Laboratory in Grenoble, France, he stumbled upon the Quantum Hall Effect. This effect describes how, under strong magnetic fields and low temperatures, electrical resistance changes in extremely thin materials in discrete steps, as determined by the laws of quantum mechanics. Five years later, von Klitzing, who at the time was the director of the Max Planck Institute for Solid State Research in Stuttgart, received the Nobel Prize in Physics for this discovery. In his lecture, the physicist mentioned that there are now nearly 19,000 publications referencing the Quantum Hall Effect. Additionally, his insight has contributed to three other Nobel Prizes and the redefinition of the kilogram by the International Bureau of Weights and Measures about six years ago.

Prof. Klaus von Klitzing vividly described how, at the age of 36, he worked in the lab at night to conduct his energy-intensive experiments using the most affordable night-time electricity. He immediately recognized his groundbreaking discovery as such, he said. His logbook with the notes from that night is now on display at the German Museum in Bonn. Based on the effect he discovered, all precision measurements of electrical resistances worldwide are now conducted relative to the so-called “von Klitzing constant” – a physical constant for resistance.

The green-lit Audimax from above.

“The sudden existence of a resistance that was always the same was so unexpected that it was initially difficult to publish the findings,” von Klitzing recalled. “I am proud of having my own constant.”

The New Kilogram

But what could be next for a scientist after receiving the Nobel Prize? Around 40 years ago, the impact “his constant” would have on metrology – the science of measurement – was unimaginable for von Klitzing. In 2018, he was invited to the General Conference of the International Bureau of Weights and Measures: “Emotionally it was the most important conference of my life. The delegates from 58 member states were thrilled and unanimously voted to redefine fundamental units of measurement.” Since 20 May 2019, the kilogram has been redefined based on the Planck constant. The original kilogram, made of a platinum-iridium alloy and secured as a prototype since 1889 in a vault deep underground at the International Bureau of Weights and Measures near Paris, had served its time. The von Klitzing constant links the Planck constant with the elementary charge and is used in the determination of electrical resistances.

Prof. Klaus von Klitzing's lecture impressively demonstrated the importance of fundamental research and how the Nobel laureate's discoveries have contributed to the fact that all units of measurement established in the International System of Units are now based on physical constants. Numerous questions following the lecture showed the great interest of the audience in the Nobel laureate's experiences, who also explained how the new kilogram can be realized experimentally – including through the creation of a special silicon sphere.

About the “Initial Spark” Lecture Series

Swedish chemist Alfred Nobel, inventor of dynamite and founder of the Nobel Prize, experimented with explosives in mining in the 1860s at the Dorstfeld mine in Dortmund. To safely detonate nitroglycerin, he developed the so-called “Initial Spark”, or “Initialzündung” in German, in 1863. Thus, the title of the lecture series refers to this phase of Nobel's experimentation in Dortmund. The series is supported by the Wilo-Foundation. Previous guests have included Prof. Frances Arnold (Nobel Prize in Chemistry 2018), Prof. Erwin Neher (Nobel Prize in Medicine 1991), Prof. Benjamin List (Nobel Prize in Chemistry 2021), Prof. Reinhard Genzel (Nobel Prize in Physics 2020), and Dr. Irina Scherbakowa (Nobel Peace Prize 2022 for the human rights organization Memorial).

To top of page