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These changes in the material, which had never been seen before, were detected with SLAC’s instrument for ultrafast electron diffraction (UED), a high-speed “electron camera” that probes the motions of a material’s atomic structure with a powerful beam of very energetic electrons.
“We were looking for other effects in our experiment, so we were taken by complete surprise when we saw that we can write and erase domain walls with single light pulses,” says Xijie Wang, head of SLAC’s UED group.
Anshul Kogar, a postdoctoral researcher in Gedik’s group, says, “The domain walls are a particularly interesting feature because they have properties that differ from the rest of the material.” For example, they might play a role in the drastic change seen in tantalum disulfide’s electrical resistance when it’s exposed to ultrashort light pulses, which was previously observed by another group.
SLAC staff scientist Xiaozhe Shen, one of the study’s lead authors on Wang’s team, says, “UED allowed us to analyze in detail how the domains formed over time, how large they were and how they were distributed in the material.”
The researchers also found that they can fine-tune the process by adjusting the temperature of the crystal and the energy of the light pulse, giving them control over the material switch. In a next step, the team wants to gain even more control, for example by shaping the light pulse in a way that it allows generating particular domain patterns in the material.
“The fact that we can tune a material in a very simple manner seems very fundamental,” Wang says. “So fundamental, in fact, that it could turn out to be an important step toward using light in creating the exact material properties we want.”
Intensity patterns recorded with SLAC’s “electron camera” showed researchers how the atomic structure of a tantalum disulfide crystal responded to laser flashes, switching from an alpha state (left) to an alpha/beta state (right) and back. The intensity patterns were used to reconstruct the atomic structure.
Additional contributions to this study came from Harvard University. The project was funded by the DOE Office of Science and the Gordon and Betty Moore Foundation.
SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the U.S. Department of Energy's Office of Science.
SLAC National Accelerator Laboratory is supported by the Office of Science of the U.S. Department of Energy. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.
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