The superconductivity of layered graphene is surprisingly strange

Physicist here. The superconductivity in layered graphene is indeed surprisingly strange, but this popular article may not do it justice. Here are some older articles on the same topic that may be more informative:

https://www.quantamagazine.org/how-twisted-graphene-became-t...,

https://www.quantamagazine.org/a-new-twist-reveals-supercond....

Let me briefly say why some reasons this topic is so interesting. Electrons in a crystal always have both potential energy (electrical repulsion) and kinetic energy (set by the atomic positions and orbitals). The standard BCS theory of superconductivity only works well when the potential energy is negligible, but the most interesting superconductors --- probably including all high temperature ones like the cuprates --- are in the regime where potential energy is much stronger than kinetic energy. These are often in the class of "unconventional" superconductors where vanilla BCS theory does not apply. The superconductors in layered (and usually twisted) graphene lie in that same regime of large potential/kinetic energy. However, their 2d nature makes many types of measurements (and some types of theories) much easier. These materials might be the best candidate available to study to get a handle on how unconventional superconductivity "really works". (Besides superconductors, these same materials have oodles of other interesting phases of matter, many of which are quite exotic.)

I think everything we don't have a model for is surprisingly strange. Gravity only seems "normal" because we've been teaching a reasonable model for it for hundreds of years - Aristotle thought things fell to the ground because that was "their nature", but thought it quite weird. X-Rays seem bonkers unless you've grown up with them, and there is something deeply unnerving about genetics, quantum and even GenAI until you've spent some time pulling apart the innards and building an explainable model that makes sense to you. And even then it can catch you out. More ways to explain the models help normalise it all - what's now taught at 9th grade used to be advanced post-doc research, in almost every field. And so it goes on.

2D superconductors don't make much sense because, as the article says, theory is behind experimentation here. That's also why there is both incredible excitement, but also a worry that none of this is going to stack up to anything more than a bubble. My old Uni (Manchester) doubled down hard on the work of Geim and Novoselov by building a dedicated "Graphene Institute", after they got the Nobel Prize, but even 15 years after that award most people are still trying to figure out what does it all actually mean really? Not just in terms of the theory of physics, but how useful is this stuff, in real world usage?

It'll settle down in due course. The model will become apparent, we'll be able to explain it through a series of bouncing back between theory and experiment, as ever, and then it won't seem so strange any more.

I'm not sure that'll ever be true of quantum computing for me, but then I am getting a bit older now...

My interest with these overlapping lattices is the creation of fractional electric charges (Hall effect) and through, essentially, Moiré patterns. The angle of alignment will make a big effect.

Let me make an artifact to demonstrate… brb

Slightly different preprint variants:

https://arxiv.org/abs/2406.13742

https://arxiv.org/abs/2406.13740v2

This is exciting, sounds like new theory incoming (or possible way to test existing string/other theories?). I'd love to see PBS Spacetime or some other credible outlet explain the details of the experiment / implications for mere mortals.

Is this exactly 1.1 degrees?

Or is it 1.09955742876?

What I mean -- did they round up, is there some connection to universal constants?

Edit: I don't understand where the 1.1 degrees comes from. Why is it 1.1 and not something else...