This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: An electron is supposed to be indivisible. It carries one fundamental unit of electric charge, and every electron is exactly the same.
But under extreme conditions, large numbers of electrons act together and give rise to new quantum objects called quasiparticles. These act as if they carry only a fraction of an electron's charge, making them one of the strangest phenomena in modern physics. Such extreme conditions occur during something called the "quantum Hall effect": When electrons are confined to two dimensions and exposed to an intense magnetic field at very low temperatures, they stop behaving like individual particles and instead organize into highly ordered quantum states.
In some of these states, the collective motion of many electrons gives rise to quasiparticles with fractional electric charges. For years, researchers have relied on complex experiments to detect these fractional charges. Now, a team led by Mitali Banerjee, professor at the Laboratory of Quantum Physics, Topology and Correlations at EPFL, has shown that a much simpler graphene device can allow scientists to study many more electron states.
The findings are published in the journal Nature Physics. The device is built from bilayer graphene, a material made of two sheets of carbon atoms. Using electrical gates, the researchers created a tiny energy hill called an antidot.
Quasiparticles move around this energy hill in well-defined paths. Changing the magnetic field or gate voltage causes them to tunnel across the device at regular intervals. Each tunneling event produces a small oscillation in the electrical signal.
By measuring the spacing between these oscillations, the researchers can work out the charge of the quasiparticles. In other words, the antidot acts like an extremely sensitive charge meter. The measurements revealed quasiparticles carrying one-third of an electron's charge at several quantum Hall states, including the states 4/3, 5/3 and 7/3.
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