Was the quantum Hall effect discovered in Grenoble?

The Hall effect in one paragraph

Send an electric current along a thin strip of conductor and place it in a magnetic field at right angles to the strip. The field pushes the moving charges sideways, so a small voltage appears across the strip. This is the Hall effect. Divide that sideways voltage by the current and you get the Hall resistance. In ordinary conditions it grows steadily as the magnetic field gets stronger.

What happened in Grenoble

Grenoble had what von Klitzing needed: very strong magnetic fields. The lab grew out of Louis Néel’s magnetism research; in 1970 it became a national facility for intense magnetic fields, from 1972 it worked with the Max Planck Institute for Solid State Research in Stuttgart, and in 1974 its electrical power was raised to 10 megawatts. The Nobel Foundation calls the place simply the high-field magnet laboratory in Grenoble.

According to the history of the LNCMI, the national high magnetic field laboratory that runs the site today, von Klitzing discovered the effect there on the night of 4–5 February 1980. The Nobel presentation speech also places his work on the Hall effect in Grenoble in February 1980.

His samples were silicon transistors of a type called MOSFET, in which the electrons that carry the current are confined to an extremely thin layer, effectively two-dimensional. The paper he later published with Gerhard Dorda of Siemens and Michael Pepper of the Cavendish Laboratory in Cambridge describes measurements in a field of 18 tesla at a temperature of 1.5 kelvin, only a degree and a half above absolute zero.

What he saw: flat steps

Under those conditions the Hall resistance did not rise smoothly. It climbed in steps, with flat plateaus where it hardly changed at all. On one plateau the paper reports 6,453.22 ± 0.10 ohms, averaged over all the samples measured, and the value did not depend on the size or shape of the device.

That was the remarkable part. The Nobel Foundation explains that the steps correspond to whole-number multiples of a combination of two fundamental constants, the charge of the electron, e, and Planck’s constant, h. A resistance that depends only on constants of nature, and not on the material or its imperfections, is something a physicist can measure anywhere and expect to get the same answer.

The paper, titled “New Method for High-Accuracy Determination of the Fine-Structure Constant Based on Quantized Hall Resistance”, was received by Physical Review Letters on 30 May 1980 and published on 11 August 1980. As the title shows, the authors first presented it as a way to measure a fundamental constant precisely.

The Nobel Prize of 1985

On 16 October 1985 the Royal Swedish Academy of Sciences announced the Nobel Prize in Physics for von Klitzing alone, “for the discovery of the quantized Hall effect”. The press release stressed the precision: the plateaus deviate from whole-number values by less than one part in ten million. That, it said, meant the effect could be used as a standard of electrical resistance, and national metrology laboratories in several countries were already studying it for the purpose.

From Grenoble to the definition of the ohm

That is what happened. In 1988 the International Committee for Weights and Measures adopted a conventional value for the von Klitzing constant, R_K = h/e²: exactly 25,812.807 ohms, denoted R_K-90, to be used from 1 January 1990, “and not before”. From that date laboratories around the world adjusted their reference resistors to agree with it. The plateau von Klitzing measured in Grenoble is a quarter of this value.

There was a catch. As Germany’s national metrology institute, the PTB, explains, the 1990 value was a convention that did not fit the International System of Units. That changed on 20 May 2019, when the revised SI came into force with fixed, exact values of Planck’s constant and the elementary charge. Since then the von Klitzing constant follows directly from them, and quantum Hall resistors realise the ohm within the SI itself. How the revised SI works is explained on our sister site, sevres.science.

Why it is a Grenoble story

So the precise answer to the question is this: the effect was discovered in Grenoble, by a scientist from Würzburg, in a laboratory run with German partners, and it was published with co-authors from Germany and Britain. That mix is typical of Grenoble, where international collaboration on big instruments is the norm, as the ESRF and the ILL show. The high-field laboratory is still there: in 2009 it merged with the pulsed-field lab in Toulouse to form the LNCMI, and its new 43-tesla hybrid magnet, resumed in 2011, was completed in 2024.

The city’s wider tradition of magnetism and physics, from Louis Néel to the big machines, is told on City & Region. For a different side of Grenoble’s physics, see Why does Grenoble have a nuclear reactor that makes no electricity?