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Science Technology

Physics Experiment With Ultrafast Laser Pulses Produces a Previously Unseen Phase of Matter (phys.org) 42

Posted by BeauHD from the never-before-seen dept.
An anonymous reader quotes a report from Phys.Org: Adding energy to any material, such as by heating it, almost always makes its structure less orderly. Ice, for example, with its crystalline structure, melts to become liquid water, with no order at all. But in new experiments by physicists at MIT and elsewhere, the opposite happens: When a pattern called a charge density wave in a certain material is hit with a fast laser pulse, a whole new charge density wave is created -- a highly ordered state, instead of the expected disorder. The surprising finding could help to reveal unseen properties in materials of all kinds.

The experiments made use of a material called lanthanum tritelluride, which naturally forms itself into a layered structure. 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. The study has been published in the journal Nature Physics.
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Physics Experiment With Ultrafast Laser Pulses Produces a Previously Unseen Phase of Matter More

Physics Experiment With Ultrafast Laser Pulses Produces a Previously Unseen Phase of Matter

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  • Humans are amazing! (Score:3)

    by Futurepower(R) ( 558542 ) on Tuesday November 12, 2019 @10:37PM (#59408968) Homepage
    We are seeing faster and faster development of technological understanding.

    • Re: (Score:3)

      by rtb61 ( 674572 )

      What is going on, is differing frequencies of interaction being applied at the same time. One frequency being the frequency of the light and the other frequency being the frequency of the pulses.

      So if you wanted to make an advanced plane fall out of the sky, you target it transistors, with a frequency energy that will pass through everything and then pulse it at the frequency required to alter the charge state of the transistor, shifting it from zero to one. This is as a result the different energy states,

  • That if an electrical charge is applied the current will go in a different direction?

  • ...a rainbow-colored corridor of lights opens up, you are pulled in, loud swooshy sounds surround you, and then finally you spot something and say, "My God, it's full of stars!"

  • Seeing how a change is observed for a few picoseconds, was the change caused by observation?

    Does it change when not observed or is it just the observation of a ''crooked dealer''?

  • Poking holes in the simulation...

  • > Normally, all stable materials are found in their minimum energy states—that is, of all possible configurations of their atoms and molecules, the material settles into the state that requires the least energy to maintain itself. But for a given chemical structure, there may be other possible configurations the material could potentially have, except that they are suppressed by the dominant, lowest-energy state.

    > By knocking out that dominant state with light, maybe those other states can be re

  • the pulse is short, not fast.

    pedantic is my middle name
    and i wear it with fucking pride

    • Re: (Score:1)

      by meglon ( 1001833 )
      Well it is a laser.... making it move at the speed of light.... which is pretty fast. So it's both short and fast, and may very well taste like cherry lime-ade.

  • So this is what it looks like to watch a Russian troll farm argue with itself over American politics?

    I'm sure I've seen it before. Maybe less obvious?

  • "Water, with no order at all" (Score:4, Interesting)

    by BAReFO0t ( 6240524 ) on Wednesday November 13, 2019 @01:59AM (#59409266)

    I'm sorry, what?

    Water is a polar molecule. Or more precisely, oxygen ions in hydrogen ions, with vague affinities.

    In a polar container or with polar objects submerged in it, or a magnetic field in the environment, it definitely has some order to it. E.g. a small layer of one type of ions close to the polar object/wall.

    I would have chosen a better example. :)

    Note: don't get your hopes up, esoterics. Homeopathy is still bullshit. You still need a therapy.

  • Now the only thing left to do is to think how can we make a weapon out this magnificent future tech!

  • Seems like an excitation of a many particle system (Score:5, Interesting)

    by gotan ( 60103 ) on Wednesday November 13, 2019 @06:40AM (#59409506) Homepage

    As far as i understand it:

    They hit their material with a laser, it transitioned to another (higher energy) state, and that state decayed again (quickly).

    An excitation can be observed e.g. in a hydrogen atom: Hitting it with light of just the right frequency excites it to a higher energy state, i.e. the electron goes into a (energetically) "higher" quantum state and that state decays emitting light.

    In the experiment it's not a hydrogen atom, but a many particle system. In such systems, e.g. in crystals, the lowest energy state may be one in which the electrons (and nuclei) obey a macroscopic order stretching the whole crystal, and arrange in a highly coordinated state. One commonly known example of such behavior is ferromagnetism, where due to quantum mechanical (exchange) interaction the valence electrons of a crystal domain preferably have their spin point in the same direction to reach lowest energy state (that way the exclusion principle reduces electric interaction between same charged electrons).

    One such many particle state is a charge density wave. There the electrons are not evenly spread across all (equivalent) lattice sites, instead their density may for example alternate between high and low, alternating from layer to layer in a lattice(*). In their material that is the lowest energy state. They managed to get the material to another energy state, where the charge density wave is in a perpendicular direction, and they showed, that that state quickly decays and the crystal goes back to the ground state.

    I think the remarkable thing here is, that they observed quantum state transitions for a larger (many particle) system.

    As for the "unseen state of matter": They managed to get LaTe3 to a state it usually isn't in, but there are similar materials (replacing La with another element) where that transition happens at a specific temperature. As usual the headline is disappointingly misleading.

    (*):
    The crystal structure they work with has one direction that is "special" compared to the other two.

    • Still, it could be useful for better understanding of inertial confinement fusion reactions. Using heavy H2O or CH4 instead of LaTe3 may show more efficient ways to initiate a fusion reaction if they can pulse it properly. Any new knowledge in this area is good news for nuclear engineers.

      • Re: (Score:2)

        by gotan ( 60103 )

        I honestly don't see how.

        The experiments are concerned with the (mostly) electronic ground state in crystal lattices, i don't see how that can have a significant effect on the nuclei that would facilitate fusion reactions.

    • I think the remarkable thing here is, that they observed quantum state transitions for a larger (many particle) system.

      How is that remarkable? You yourself started off with the example of hitting hydrogen with an energy burst and getting a photon out of it when it drops back to the ground state. All macroscopic lasers work this way, inducing energy state transitions in a chunk of material, then preferentially shoving the photons out the same side when the whole block of material transitions back to the ground state simultaneously. Maybe you meant it's remarkable to see this particular type of state transition in a macros

  • This is pretty interesting stuff - I'm wondering if this would work on non-perfect crystalline structure. Say a metal part is starting to suffer from fatigue due to age - can it be zapped with a laser to bring it to a higher energy state, where it presumably would form a perfect lattice structure, then decay back into its normal state - and retain a perfect structure there as well?

    If that works, it could be amazing. Maybe even spawn new methods of 'welding' or assembly in manufacturing.

    Any metallurgists o

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