Ultrafast laser pulses produce a previously unseen phase of matter | Hacker News Reader

Ultrafast laser pulses produce a previously unseen phase of matter

phys.org

195 pointsnerdy33 comments

New phases of matter uncovered by ultrafast laser pumping is more common than you might think.

Dumping a bunch of energy into a system in less than 30fs (30 x 10^-15s) creates a profoundly non-equilibrium situation. Whatever phase of matter you observe right after will likely have no equilibrium analogue.

> The perpendicular version of the CDW that appears after the burst of laser light has never before been observed in this material, Gedik says. It "just briefly flashes, and then it's gone," Kogar says, to be replaced by the original CDW pattern which immediately pops back into view.

The interesting bit is here:

> Gedik points out that "this is quite unusual. In most cases, when you add energy to a material, you reduce order."

That is what's great about this. New phases of matter in ultrafast experiments are old news.

It's upsetting. Reminds me of when the CERN people made that paper about modulated plasma wave acceleration, and pretended they were the first to do it, or at least the popular press did. You only realize it when it's your field (as do I here) but we in physics ought to talk to each other more.

To be fair, the authors are not claiming that this is the first time, only that this is the first time in this material. As you say, the press makes it up to be different than it is.

Anyone following science (or tech, or medicine, or anything) news will (ought to) realize how over-hyped and fluff-heavy every press release is. Real breakthroughs are very few and far between, because progress seems incremental. And because usually those breakthroughs are unseen, uninteresting, not even press-release worthy, because we haven't realized its potential. Then someone tries out that new thing for that old problem, and gets maybe decent numbers, usually just meh. Then slowly it builds, and then eventually comes the paradigm shift. But at that point it's the waiting game, slow march of better and better engineering, getting better trade offs, and so on.

An example I'd encountered was a set of papers out of the US Naval Research Lab on fuel synthesis (electricity + seawater => hydrocarbon jet fuel). The citations dated only to the mid/late 1990s, though it turns out prior art and development date to at least the 1960s (for electically-based fuel synthesis), the 1930s if Fischer-Tropsch synthesis from coal is included.

https://old.reddit.com/r/dredmorbius/comments/22k71x/us_navy...

The impression generated was tremendously misleading.

I ended up digging into the history myself:

https://old.reddit.com/r/dredmorbius/comments/29ihl7/us_doe_...

https://old.reddit.com/r/dredmorbius/comments/28nqoz/electri...

"New phases of matter uncovered by ultrafast laser pumping is more common than you might think."

Did not know this, until now! (But then again, I am not a professional Physicist, so I claim exemption from having to know!)

Anyway, very interesting!

Original MIT press release of which this is a word-for-word copy: https://news.mit.edu/2019/light-orders-exotic-material-1111

Actual letter in Nature Physics: https://www.nature.com/articles/s41567-019-0705-3

Sci-Hub link to pdf http://sci-hub.tw/https://www.nature.com/articles/s41567-019...

Wow, this makes way more sense than in the press release. Scihub is a treasure.

I'm not from academia but is it unusual to have 21 authors on a paper?

My observations: I rarely see it in computer science related papers. I often see it in biology / medicine papers (but I don't see lots of those papers)

If you wonder what 21 people do for one paper, they have mentioned it in the paper pdf (look for the scihub link here in the comments) on the last page: Only two people actually wrote the paper with input from a lot of others, supervised by yet another one.

Lab experiments involve huge amount of support people who have to do really specific work for each experiment.

Listed authors of reports are a bit like credits in film, and similarly, in fields/production where you have a lot of special-effects/complicated scientific apparatuses/huge custom built computer clusters for doing the analysis, you get a lot of supporting personell that you might want to credit.

Oarticle physics papers sometimes list a huge number of authors, record I think is 5154 for a paper from an LHC collaboration titled "Combined Measurement of the Higgs Boson Mass in pp Collisions at √s=7 and 8 TeV with the ATLAS and CMS Experiments"

Nature wrote about it https://www.nature.com/news/physics-paper-sets-record-with-m...

Just when you think Physics has little left to discover, something you never expected creates a whole new avenue to explore.

"When I began my physical studies [in Munich in 1874] and sought advice from my venerable teacher Philipp von Jolly...he portrayed to me physics as a highly developed, almost fully matured science" - Max Planck

I don't think physics will ever be fully matured. There is always a "Why?" that needs an answer.

I'm not sure that "Why?" is always going to be a physics question, but certainly even after we understand the smallest building blocks, we will need specific models of arbitrarily complex systems where the basic rules are computationally infeasible or resistant to simple analysis.

Of course, understanding the true and most basic workings of nature will also take a lot of work, just not a literally infinite supply.

Thanks to chaos, we will probably have no shortage of computationally infeasible systems.

Though the study of those systems is often labelled by something other than 'physics'. Biology or Chemistry or Psychology or Economics etc.

What makes you think physics has little left to discover?

> The idea that two possible states of matter might be in competition and that the dominant mode is suppressing one or more alternative modes is fairly common in quantum materials, the researchers say. This suggests that there may be latent states lurking unseen in many kinds of matter that could be unveiled if a way can be found to suppress the dominant state.

How exciting! I can only daydream about the kind of discoveries to be found about matter in, say, 50 years.

I don't understand it enough to get excited - what are the potential applications?

I don't think we can comment on any applications at this time.

A lot of discoveries like these aren't exciting because of commercial potential, if that's what you mean by applications. As we discover more states and more properties of these states, as we develop technologies to persist these states for longer than a fleeting amount of time, we might discover interesting properties which may have commercial uses. Sometimes, the technologies developed to create/contain such exotic materials themselves tend to have commercial applications. That's how it is with the interplay of science and technology with the economy.

In some materials, this hidden configuration might have interesting properties. It could even be (quasi)stable once the original pattern is suppressed. So, novel superconductors or metamaterials, maybe?

My guess would be maybe in this new state, some metals might be more likely to alloy with others, so we'll have lots of fun new materials with strange properties. Maybe even find a new super conductor or two.

I don't think anyone can predict the applications because creating new materials could have many, or almost no, novel or useful properties. Look at how many different ways we can manipulate iron and create different properties, now there might be even more. Or maybe it isn't stable in bulk atmospheric amounts, but can be held under pressure and has some unique property to make it suitable for computing, or detecting certain kinds of energy or radiation, or forms piezoelectric properties or who knows. Maybe it can be used in optical data processing or amplifying.

Most likely this isn't going to revolutionize our world, but there is always that small chance, and we will certainly find some use for these novel states of matter somewhere, if not just more physics experiments.

Excerpt:

"In this material, a wavelike pattern of electrons in high- and low-density regions forms spontaneously but is confined to a single direction within the material. But when hit with an ultrafast burst of laser light—less than a picosecond long, or under one trillionth of a second—that pattern, called a charge density wave or CDW, is obliterated, and a new CDW, at right angles to the original, pops into existence.

This new, perpendicular CDW is something that has never been observed before in this material. It exists for only a flash, disappearing within a few more picoseconds. As it disappears, the original one comes back into view, suggesting that its presence had been somehow suppressed by the new one."

My thoughts:

The first thought that comes to mind is "superposition"... The second thought that comes to mind is "possible higher-dimensional and/or phase-shifted view of the substructure of matter" (in this case, lanthanum tritelluride)... Even if neither of these things turn out to be the case, the phenomena is fascinating!

Exciting. Could we build a laser-pulsed Charge Wave computer?

Is this going to end up having applications for integrated circuit manufacturing?

Holy shit, Pablo is on fire!

Laugh-a while you can, monkey-boy.

> "What if all you need to do is shine light on a material, and this new state comes into being?"

Wonder if it's related to photosynthesis?

It's not. Photosynthesis is a chemical reaction where light provides energy and that only involves gas, liquid and solid states of matter.

These guys are talking about entirely different states of matter.

I seem to remember there were some mysteries around how photosynthesis works. Although looking at wikipedia it seems quite comprehensively mapped out now

This experiment only involves solids. The new phase is a different electronic structure of the same crystal.

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