Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Redefining the kilogram and the ampere

29.09.2011
New research using graphene presents the most precise measurements of the quantum Hall effect ever made, 1 of the key steps in the process to redefine 2 SI units

Groundbreaking research by the National Physical Laboratory's (NPL) Quantum Detection Group and an international team of collaborators is underpinning the biggest change in the Système Internationale d'unités (SI Units) since the system began 50 years ago.

It has long been the goal of scientists to relate all of the unit definitions to fundamental constants of nature, making them stable and universal, and giving them closer links to each other and the quantities they measure.

Key units to be redefined are the kilogram (mass) and the ampere (electric current). Presently the kilogram is defined by a physical lump of platinum-iridium and the ampere is defined via the force produced between two wires.

The goal is to define the kilogram in terms the Planck constant h and the ampere in terms of the electron charge e.

Making this change relies on the exactness of the relationships that link these constants to measurable quantities.

The quantum Hall effect defines a relationship between these two fundamental physical constants. Experiments are needed to test the quantum Hall effect in different materials in order to prove whether or not it is truly universal.

Until recently the effect was exclusively observed in a few semiconductor materials. A few years ago the quantum Hall effect was also observed by the same team in graphene, a completely different type of material with a very different electronic structure.

This research directly compared the quantum Hall effect in graphene with that observed in a traditional semiconductor material. Graphene is hotly tipped to surpass conventional materials in many important applications, partly due to its extraordinary electrical properties.

The results confirmed that the quantum Hall effect is truly universal with an uncertainty level of 86 parts per trillion, supporting the redefinition of the kilogram and ampere. The quantum Hall effect in graphene is so good that it should be the material of choice for quantum resistance metrology.

The discovery was today highlighted in Nature as a leading piece of research.

JT Janssen, NPL Science Fellow and the lead author of the research, said: "Many metrology laboratories around the world have been striving to do this experiment and it is a real achievement that the NPL team and its co-workers were the first to get this key result. It turns out that the quantum Hall effect in graphene is very robust and easy to measure - not bad for a material that was only discovered six years ago."

The research was conducted in collaboration with the Bureau International des Poids et Mesures, Chalmers University of Technology (Sweden), Lancaster University (UK) and Linköping University (Sweden).

Read paper in New Journal of Physics: http://iopscience.iop.org/1367-2630/13/9/093026/

David Lewis | EurekAlert!
Further information:
http://www.npl.co.uk/

More articles from Physics and Astronomy:

nachricht Only an atom thick: Physicists succeed in measuring mechanical properties of 2D monolayer materials
17.01.2018 | Universität des Saarlandes

nachricht Black hole spin cranks-up radio volume
15.01.2018 | National Institutes of Natural Sciences

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

Im Focus: Room-temperature multiferroic thin films and their properties

Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.

Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...

Im Focus: A thermometer for the oceans

Measurement of noble gases in Antarctic ice cores

The oceans are the largest global heat reservoir. As a result of man-made global warming, the temperature in the global climate system increases; around 90% of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

Polymers Based on Boron?

18.01.2018 | Life Sciences

Bioengineered soft microfibers improve T-cell production

18.01.2018 | Life Sciences

World’s oldest known oxygen oasis discovered

18.01.2018 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>