A new study reveals that the response of quantum materials to light is more complex than previously assumed. Using ultrafast X-ray pulses at the X-ray free electron laser SwissFEL, researchers found that the surface of a layered manganese oxide reacts differently than the bulk when its orbital order is disturbed. These results challenge the idea that light-induced changes happen uniformly and suggest that the path from order to disorder is shaped by local differences inside the material.
In certain materials, the electrons arrange themselves in a well-defined, ordered pattern. This internal order can influence everything from how the material conducts electricity to how it responds to magnetic fields. One example is the layered manganese oxide and quantum material La0.5Sr1.5MnO4, in which electrons of manganese atoms arrange themselves into a regular pattern – known as orbital ordering – leading to distinctive electronic and magnetic behaviour.
Researchers are increasingly interested in how light can be used to understand and control the orbital state of these materials. With the right kind of light pulse, it may be possible to switch or reshape their properties at incredible speeds. Therefore, understanding how these materials switch is an important step to making devices.
In many devices, surfaces of and interfaces between materials are known to play a major role in the device properties. Yet until now, it has not been possible to measure how quantum materials change at the surface when switched at high speeds by light. Previous studies have only captured the average response over the whole crystal.
In this study, a team of scientists led by Aarhus University asked if the average response measured to date accurately captures the processes that occur at the surface, which will be relevant for any device. Remarkably, they found that they did not.
Read more on the PSI website
Image: Using ultrafast X-rays from SwissFEL, scientists have revealed unexpected light responses in quantum materials
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