Graphene device measures fractional electric charges carried by some of quantum physics' strangest objects
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.
A team of researchers from EPFL has developed a simple graphene device capable of measuring fractional electric charges carried by quasiparticles in quantum Hall states. Quasiparticles, which emerge from the collective behavior of electrons, have been observed to exhibit unusual fractional charge values under certain conditions.
The researchers utilized bilayer graphene, a two-layered carbon material, along with electrical gates to create an 'antidot' structure. This unique configuration acts as an energy hill that guides the movement of quasiparticles, causing them to tunnel across the device at regular intervals. By measuring the spacing between these oscillations in the electrical signal, the researchers were able to determine the charge of the quasiparticles.
Notably, the device detected quasiparticles carrying one-third, two-thirds, three-fifths, four-thirds, five-thirds, and seven-thirds of an electron's charge at various quantum Hall states. These findings, published in the journal Nature Physics, demonstrate the potential of the graphene antidot design for investigating other topological quantum states and potentially contributing to the development of quantum technologies.
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