A New Kilogram is coming up
And how the father of the von Klitzing constant is concerned with this
In 1980, Nobel laureate in Physics, Klaus von Klitzing*, discovered the ‘quantum Hall effect’ during a night in France drinking red wine in his laboratory. If von Klitzing wasn’t a physician, he would certainly be a stand up comedian. During his talk, he took us through his career and scientific discoveries and explained why the kilogram as we know it will change in 2019.
During his childhood Von Klitzing preferred to solve equations in mathematics and physics, rather than play with his toys on Christmas Day. During his time as a student, he would bribe the security guard at his university to be able to stay and work during the night. Finally, he completed his PhD thesis at 29 years old, and finished his habilitation six years later.
Since 1985, Von Klitzing has been the director of the Max Planck Institute for Solid State Research. It was this same year that Von Klitzing won the Nobel Prize of Physics for the quantum Hall effect. The quantum Hall effect is a quantum-mechanical version of the Hall effect, observed in two-dimensional electron systems subjected to low temperatures and strong magnetic fields. The fractional quantum Hall effect is more complicated, as its existence relies fundamentally on electron–electron interactions. It is understood as an integer quantum Hall effect, although not of electrons but of charge-flux composites known as composite fermions.**
The quantization of the Hall conductance has the important property of being exceedingly precise to measure voltage dynamics. At low temperatures and strong magnetic fields, a Hall voltage appears in current-carrying semiconductors (such as copper, gold etc.) that changes stepwise – along the so-called “von Klitzing constant”. Actual measurements of the Hall conductance have been found to be integer or fractional multiples of to nearly one part in a billion. This phenomenon is known as “exact quantization”. It has allowed for the definition of a new practical standard for electrical resistance, based on the resistance quantum given by the von Klitzing constant:
RK = h/e2 = 25812.807557(18) Ω.
Since 1990, a fixed conventional value RK-90 is used in resistance calibrations worldwide. The integer of the Hall conductance was originally predicted by Ando, Matsumoto, and Uemura in 1975, on the basis of an approximate calculation which they actually did not believe to be true. Several researchers subsequently observed the effect in their experiments. It was only in 1980 that Klaus von Klitzing, working with silicon-based samples at the high magnetic field laboratory in Grenoble, sipping a glass of red wine, made the unexpected discovery that the Hall conductivity was exactly quantized. His motivation was quite simple, he ‘wanted to understand something that was unclear’ to him. For the discovery of exact integer, he was awarded with the Nobel Prize in Physics 1985. The Nobel ceremony was much more enjoyable to attend as a guest than a winner, Von Klitzing remembered during his talk. He continued: ‘There are two ways to get a Nobel Prize: either through research, or through money. As Von Klitzing mentioned, if your bid is high enough at one of the auctions, you can take the Prize home.
But how does this refer to the prototype kilogram? Whose slow decay cannot be stopped even by complex mechanic protection devices in its storage near Paris. Are von Klitzing’s ideas capable of solving the problem of the weight-losing kilogram? Klaus von Klitzing is one of two living Nobel laureates who have given a name to a constant. As a great mind and an expert the International Committee for Weights and Measures invited him to be part of defining process for a new metric system.
In 2019, the kilogram will get more accurate. For 125 years, a salt-shaker-sized cylinder housed at the Bureau International des Poids et Mesures (BIPM) in Paris, and weighing exactly a kilogram served as the definition of the measure. However, an international conference of heads of metrology institutes decided, on October 19 2017 in Sevres, France, that the kilogram will no longer be pegged to this cylinder made of 90% platinum and 10% iridium. During the past 60 years, several standard units including the second, the metre or the ampere amongst others, have all ceased to be defined by physical objects. One metre, for instance, was a platinum-iridium bar of that measure. Essentially, the units were freed from being defined on the basis of artefacts, as these being objects, were subject to wear and tear and sources of eventual error. The new artefacts, according to the International Committee for Weights and Measures, ought to derive from the constants of nature that are all interdependent.
The kilogram was the only one among the units still linked to a real object. The scientific community is now set to redefine the kilogram in terms of the Planck constant, the second and the metre. The newly defined kilogram constant will unite the Max Planck Constant with Einstein’s famous equation. Von Klitzing is not only dedicated to his research but he is also passionate about promoting the development of scientific knowledge.
“The Nobel Prize to me is an obligation to the commitment of promoting enthusiasm for science,” says the father of the von Klitzing constant.
The Klaus von Klitzing Prize for particularly dedicated teachers of science subjects is intended to honor teachers who, through their dedication and creativity, help inspire students to work and think scientifically.
* a German physicist (born 28.06.1943 in Schroda, Poland) and Director at the Max Planck Institute for Solid State Research, Stuttgart
** A fermion can be an elementary particle, such as the electron, or it can be a composite particle, such as the proton.