Scientists have created superconducting transistors that remain superconducting even under powerful magnetic fields that normally destroys the effect.
These findings could lead to more robust quantum computers and to ultra-sensitive magnetic sensors that can operate even in extremely high magnetic fields, researchers say.
Superconductors conduct electricity without dissipating energy. Superconductivity depends on electrons not repelling each other as they do in ordinary materials, but instead forming weakly bonded duos known as Cooper pairs, which can flow with zero resistance.
Superconductivity vanishes whenever anything disrupts Cooper pairs, such as jostling from atoms. This means superconductivity generally disappears at high temperatures and under high magnetic fields.
Now scientists find that molybdenum sulfide, a common dry lubricant, remains superconducting even under external magnetic fields as strong as 37.5 Tesla. In comparison, the magnets in medical MRI machines reach up to 3 Tesla strong.
The researchers experimented with molybdenum sulfide transistors cooled to 12 Kelvin or less. Superconductivity can be induced in thin flakes of molybdenum sulfide by applying electric fields.
The scientists found that when molybdenum sulfide becomes superconducting, its electronic structure generates a magnetic field roughly 100 Tesla in strength. This internal field can protect the superconductor's electron pairs from weaker external magnetic fields.
"We have found a superconducting state that is super-robust against magnetic fields," says study co-author Justin Ye, a physicist at the University of Groningen in the Netherlands.
Superconductivity is key to ultra-sensitive magnetic sensors known as superconducting quantum interference devices, or SQUIDs, which are used in applications such as analyzing brain activity, medical imaging, and oil prospecting. These new findings could one day lead to SQUIDs that can operate even in powerful magnetic fields, Ye says.
Another use for magnet-resistant superconductors could be quantum computing, Ye says. The electron pairs in superconductors can form quasiparticles known as Majorana fermions, which can in theory encode data in a way that is not easily disrupted by thermal fluctuations, unlike current quantum computing systems. Magnet-resistant superconductors could make such quantum computers even more robust.
Ye notes that molybdenum sulfide belongs to a family of materials known as transition metal dichalcogenides (TMD), many of which are also superconductors. He and his colleagues will now analyze other TMDs and see if their superconductivity is similarly robust against external magnetic fields.
The scientists detailed their findings online Nov. 12 in the journal Science.
Charles Q. Choi is a science reporter who contributes regularly to IEEE Spectrum. He has written for Scientific American, The New York Times, Wired, and Science, among others.
