What's The Whole Truth About 'Less Than Whole' Electron Charges?

What is the smallest negative electric charge you can think of? Chances are that you quickly responded: 'an electron.' Indeed, ever since American physicist Robert Andrews Millikan first measured the charge of an electron nearly 80 years ago, this value has been widely regarded as the smallest basic unit of electric charge. Scientists consequently viewed the electrons that make up an electric current as a flow of negatively charged, indivisible 'balls.'

However, in 1982 American physicist , suggested that under certain conditions electric currents are comprised of small electron units, each carrying a fractional electric charge that is smaller than the fundamental charge of a single electron. According to Laughlin, these fractional charges can be a third of an electron's charge, a fifth, a seventh, a ninth, and so on.

The first evidence affirming Laughlin's theory came in 1997, when a team of Weizmann Institute scientists succeeded, for the first time ever, in measuring electronic charges equal to one-third and one-fifth that of a single electron. Headed by Prof. Mordehai Heiblum of the Joseph H. and Belle R. Braun Center for Submicron Research, the team obtained the results by creating a weak disturbance in the electric current and measuring the level of 'electric noise' produced as a result. (The increase in electric noise is proportional to the unit of electric charge: the smaller the charge, the weaker the noise.) However, recent research of the electric noise created following a stronger disturbance to the system has surprised Weizmann scientists: they found that the electric charges that produce the noise are not limited to odd-denominator fractions and can be created in any fractional size, as well as a whole electron charge.

This unexplained phenomenon is expected to trigger the curiosity of physicists worldwide. One explanation proposed by the Weizmann scientists is that the possibility of creating diverse fractional charges stems from 'cooperative interactions' between the odd-denominator fractional charges.

Prof. Mordehai Heiblum's research is supported by the Joseph H. and Belle R. Braun Center for Submicron Research, the Minerva Center for Nonlinear Physics of Complex Systems, Mr. Gabriel Katri, Switzerland, Messrs. Hermann and Dan Mayer, France, and Mr. Joseph Gurwin, Great Neck, NY.

The Weizmann Institute of Science is a major center of scientific research and graduate study located in Rehovot, Israel. Its 2,500 scientists, students and support staff are engaged in more than 1,000 research projects across the spectrum of contemporary science.