A new class of magnet that exhibits novel quantum effects | Hacker News Reader

A new class of magnet that exhibits novel quantum effects

phys.org

75 pointsbookofjoe20 comments

https://phys.org/news/2020-07-scientists-topological-magnet-...

Thanks. This is one of those times where I actually wanted such an article. That abstract was way beyond intro to QM level.

This looks really fascinating; can someone explain it to me like I'm 5? e.g. What is a "topological magnet phase"? What kind of applications might this be used for one day?

This doesn't quite get to ELI5 but hopefully is understandable to an HN audience (please feel free to correct if I've gotten anything incorrect):

"Topological" and "magnetic" are two separate concepts (see below). Phase just refers to "phase of matter" - it's used here because a material has different properties depending on the external environment (like heating a magnet beyond a certain point means it's no longer magnetic).

Topological typically refers to a "topological band structure". If you know some band theory: a material can be classed as an insulator, conductor, or semiconductor based on its band gap. A topological material is "mostly" an insulator, but has a special set of conductive channels on the surface.

Remember that an electron has this additional property of spin ("up" or "down"). The topological material is furthermore unique in that these conducting channels only conduct electrons with a particular spin. The channels are also "topologically protected", so they are immune to material imperfections and have dissipation-less conductance (kind of "superconducting" in laymen's terms, but this has a different specific meaning in physics).

Normally these topological materials are not magnetic (the topological effect is closely related to magnetic ordering), but this paper shows evidence of both, and also demonstrates that the electronic properties can be modulated by applying external magnetic field.

So combining all of this, an application of interest in computing is "spintronics", where electronics use spin current rather than charge current. Dissipation-less conductance means much more power efficient, and spin isn't volatile like charge (HDD vs RAM). Topological materials are also being explored as a promising hardware platform for quantum computing.

Thank you, this is exactly what I was looking for!

If I didn't know the context I'd think the visualization was some kabbalistic symbolism rather than scientific imagery.

A favorite sci-fi speculation of mine is that all that goofy geomancy and similar "edge of seeming like it means something" stuff in occultism is some alien intelligence attempting to send us the knowledge required to come visit them. They've found some exotic way to influence minds at a distance, or to transmit information such that minds might "resonate" with it, or something. What we end up getting are distorted glimpses of theories of quantum gravity, how to build an Alcubierre drive, etc., but we think its angels, demons, and ghosts and basically construct a cargo cult around it.

Arthur C. Clarke: Childhood's End

Rather like Lem's "His Master's Voice" (https://en.wikipedia.org/wiki/His_Master%27s_Voice_(novel))

Sounds like an Interocitor

Drop the occulty aspect and this is the premise of the 1985 movie Explorers:

A kid sees in a dream what he thinks is a circuit board, so he takes a drawing to a techy friend of his who fills in the missing parts and builds it. Turns out to create a solid floating sphere, that they get the idea to use for space travel - and end up meeting the aliens that sent them the dreams.

Trailer: https://www.youtube.com/watch?v=al75vXD6koc

(That said, the stylized form of the circuit in the dream could totally be the source of the occulty aspects - a gear looking like a sun, for example, as seen in the trailer at about 0:23, not to mention the flying aspect)

I've put that URL above instead of https://www.nature.com/articles/s41586-020-2482-7. When it comes to highly specialized papers like this one, please submit the best third-party article instead.

Papers on computing are exceptions, as are papers readable by a smart general audience. But not papers that are as specialized as this one—if people can't read them then there isn't anything meaningful to discuss; perhaps a bit of the title and that's it.

Got it.

> Quantum magnets are promising platforms for dissipationless current

Does that mean that we can produce long-distance very efficient power lines that don't need superconductors?

No, this about signals, not power.

This is a super weirdly sensationalist article. It's far too popsci to be a good read for physicists, while being far to science-jargony to be accessible to laymen.

I found the caption beneath the embedded video animation to be reasonably accessible.

Universities are forced more and more to market results to the masses. I could imagine that some poor researcher's arm got twisted into writing something for a press release and that's what came out.

I wonder if it's possible to build a language filter that excises the "named chair" names from someone's title, so:

F. Duncan Haldane, the Thomas D. Jones Professor of Mathematical Physics and the Sherman Fairchild University Professor of Physics at Princeton

becomes

F. Duncan Haldane, a Professor of Mathematical Physics at Princeton

It would vastly increase the readability of some of these things.

I am glad someone else is bothered by such titles as far as readability goes.

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