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posted by janrinok on Thursday November 14 2019, @10:10PM   Printer-friendly
from the gone-in-a-flash dept.

Arthur T Knackerbracket has found the following story:

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 discovery is being reported today in the journal Nature Physics, in a paper by MIT professors Nuh Gedik and Pablo Jarillo-Herrero, postdoc Anshul Kogar, graduate student Alfred Zong, and 17 others at MIT, Harvard University, SLAC National Accelerator Laboratory, Stanford University, and Argonne National Laboratory.

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.

Gedik explains that in ordinary materials, the density of electrons within the material is constant throughout their volume, but in certain materials, when they are cooled below some specific temperature, the electrons organize themselves into a CDW with alternating regions of high and low electron density. In lanthanum tritelluride, or LaTe3, the CDW is along one fixed direction within the material. In the other two dimensions, the electron density remains constant, as in ordinary materials.

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 new findings may help to better understand the role of phase competition in other systems. This in turn can help to answer questions like why superconductivity occurs in some materials at relatively high temperatures, and may help in the quest to discover even higher-temperature superconductors.Gedik says, "What if all you need to do is shine light on a material, and this new state comes into being?"

More information: Light-induced charge density wave in LaTe3[$], Nature Physics (2019). DOI: 10.1038/s41567-019-0705-3


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  • (Score: 3, Touché) by edIII on Friday November 15 2019, @02:59AM (1 child)

    by edIII (791) on Friday November 15 2019, @02:59AM (#920600)

    You're speaking for yourself as far as the editorial complaints and bitching about article quality.

    That, and you must have zero imagination. I had all sorts of questions here and I do expect a decent discussion.

    My take away is that they've figured out a way to access different phases of matter that never appear due to phase competition. Momentarily they're suppressing the normal phase that is present during equilibrium, and it allows a this hidden phase to appear.

    There could be all kinds of different properties for existing materials since this previously hidden phase is accessed. This particular one is highly ordered which sounds like it's modifying a solid material. What does that cause?

    This is incredibly interesting.

    --
    Technically, lunchtime is at any moment. It's just a wave function.
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  • (Score: -1, Flamebait) by Anonymous Coward on Friday November 15 2019, @03:27AM

    by Anonymous Coward on Friday November 15 2019, @03:27AM (#920603)

    > they've figured out a way to access different phases of matter

    Would you like to lick my Ice Nine?