Amazing stuff! This could be a breakthrough! Perhaps a new theory of superconductivity?
"... A 2019 prediction from theoretical physicist Ashvin Vishwanath of Harvard University, US, and colleagues suggested that multilayer graphene with alternating relative twist angles would also become superconducting, with each additional layer increasing the magic angle. This prediction has now been confirmed independently for trilayer graphene with the central layer twisted relative to the parallel top and bottom layers ...
At the predicted twist of around 1.55°, the material became a superconductor that – when its low charge density was taken into account – had the strongest electron pairing ever seen. ...
measured the twist between the bottom and middle layers and the middle and top layers in the constituent bilayers. They found that, owing to unavoidable experimental imperfections, they were 1.69° and 1.35° respectively. Nevertheless, the trilayer structure behaved as though it had an average twist angle of around 1.55°. ...
The trilayer’s superconductivity could be tuned more widely than in bilayer graphene, depending not just on the total potential of the material, but on the potential difference between the layers. This tunability allowed them to explore its superconductivity in more detail than possible with any previous superconductor. This tunability allowed them to explore its superconductivity in more detail than possible with any previous superconductor. Most notably, they found that, at points in the material’s phase diagram where the classical theory of superconductors (in which electrons are coupled by lattice vibrations) suggests that superconductivity should be most robust, it actually vanished. ...
found the same inconsistency with conventional superconductor theory. Instead, the researchers say, it supports an exotic theory of superconductivity in multilayer graphene postulated by Vishwanath’s group and University of California, Berkeley colleagues. The traditional theory also fails in high-temperature superconductors such as cuprates and pnictides, ... although the mechanism is probably different, ‘having a mechanism of how superconductivity arises from a strongly-correlated, emergent electronic mechanism ..."
At the predicted twist of around 1.55°, the material became a superconductor that – when its low charge density was taken into account – had the strongest electron pairing ever seen. ...
measured the twist between the bottom and middle layers and the middle and top layers in the constituent bilayers. They found that, owing to unavoidable experimental imperfections, they were 1.69° and 1.35° respectively. Nevertheless, the trilayer structure behaved as though it had an average twist angle of around 1.55°. ...
The trilayer’s superconductivity could be tuned more widely than in bilayer graphene, depending not just on the total potential of the material, but on the potential difference between the layers. This tunability allowed them to explore its superconductivity in more detail than possible with any previous superconductor. This tunability allowed them to explore its superconductivity in more detail than possible with any previous superconductor. Most notably, they found that, at points in the material’s phase diagram where the classical theory of superconductors (in which electrons are coupled by lattice vibrations) suggests that superconductivity should be most robust, it actually vanished. ...
found the same inconsistency with conventional superconductor theory. Instead, the researchers say, it supports an exotic theory of superconductivity in multilayer graphene postulated by Vishwanath’s group and University of California, Berkeley colleagues. The traditional theory also fails in high-temperature superconductors such as cuprates and pnictides, ... although the mechanism is probably different, ‘having a mechanism of how superconductivity arises from a strongly-correlated, emergent electronic mechanism ..."
"Moiré superlattices have recently emerged as a platform upon which correlated physics and superconductivity can be studied with unprecedented tunability. Although correlated effects have been observed in several other moiré systems, magic-angle twisted bilayer graphene remains the only one in which robust superconductivity has been reproducibly measured. Here we realize a moiré superconductor in magic-angle twisted trilayer graphene (MATTG), which has better tunability of its electronic structure and superconducting properties than magic-angle twisted bilayer graphene. ...
We find that the superconducting phase is suppressed and bounded at the Van Hove singularities that partially surround the broken-symmetry phase, which is difficult to reconcile with weak-coupling Bardeen–Cooper–Schrieffer theory. ... Our results establish a family of tunable moiré superconductors that have the potential to revolutionize our fundamental understanding of and the applications for strongly coupled superconductivity."
We find that the superconducting phase is suppressed and bounded at the Van Hove singularities that partially surround the broken-symmetry phase, which is difficult to reconcile with weak-coupling Bardeen–Cooper–Schrieffer theory. ... Our results establish a family of tunable moiré superconductors that have the potential to revolutionize our fundamental understanding of and the applications for strongly coupled superconductivity."
Here is the link to the underlying research paper:
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