Redefining the Ampere Thanks To Graphene
Measure twice, cut once is how the saying goes, and is a good one to use when making or modifying anything. For example, researchers at the National Physical Laboratory (NPL), outside of London, used it for an experiment that may lead to redefining the ampere, and even the kilogram. Many of the metric units humanity uses have been linked to physical constants or observations. The meter is defined by the speed of light and the second is tied to electron states within a ground-state cesium 133 atom. (Fun fact: when a more accurate measure of the speed of light is made, the length of the meter changes.) The kilogram and amp are two units which have not yet been tied to any fundamental constant, but the hope is to connect to them to the Planck constant and the charge of an electron, respectively. A key to doing this is to show the quantum Hall effect will universally link these two constants. The effect had only been observed in semiconductors before, but thanks to the thinness of graphene, the researchers at NPL were able to observe it elsewhere. Their results confirm the quantum Hall effect as being universal and may lead to definite values to the kilogram and ampere in the future.