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November 13, 2019 03:30 am

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

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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