Home > Press > New X-ray imaging technique to study the transient phases of quantum materials
![]() |
A crystalline lattice melting, artistically represented here as a snowflake, is superimposed upon it's coherent X-ray scattering pattern CREDIT ICFO/ Patricia Bondia |
Abstract:
The use of light to produce transient phases in quantum materials is fast becoming a novel way to engineer new properties in them, such as the generation of superconductivity or nanoscale topological defects. However, visualizing the growth of a new phase in a solid is not easy, due in-part to the wide range of spatial and time scales involved in the process.
Although in the last two decades scientists have explained light-induced phase transitions by invoking nanoscale dynamics, real space images have not yet been produced and, thus, no one has seen them.
In the new study published in Nature Physics, ICFO researchers Allan S. Johnson and Daniel Pérez-Salinas, led by former ICFO Prof. Simon Wall, in collaboration with colleagues from Aarhus University, Sogang University, Vanderbilt University, the Max Born Institute, the Diamond Light Source, ALBA Synchrotron, Utrecht University, and the Pohang Accelerator Laboratory, have pioneered a new imaging method that allows the capture of the light-induced phase transition in vanadium oxide (VO2) with high spatial and temporal resolution.
The new technique implemented by the researchers is based on coherent X-ray hyperspectral imaging at a free electron laser, which has allowed them to visualize and better understand, at the nanoscale, the insulator-to-metal phase transition in this very well-known quantum material.
The crystal VO2 has been widely used in to study light-induced phase transitions. It was the first material to have its solid-solid transition tracked by time-resolved X-ray diffraction and its electronic nature was studied by using for the first time ultrafast X-ray absorption techniques. At room temperature, VO2 is in the insulating phase. However, if light is applied to the material, it is possible to break the dimers of the vanadium ion pairs and drive the transition from an insulating to a metallic phase.
In their experiment, the authors of the study prepared thin samples of VO2 with a gold mask to define the field of view. Then, the samples were taken to the X-ray Free Electron Laser facility at the Pohang Accelerator Laboratory, where an optical laser pulse induced the transient phase, before being probed by an ultrafast X-ray laser pulse. A camera captured the scattered X-rays, and the coherent scattering patterns were converted into images by using two different approaches: Fourier Transform Holography (FTH) and Coherent Diffractive Imaging (CDI). Images were taken at a range of time delays and X-ray wavelengths to build up a movie of the process with 150 femtosecond time resolution and 50 nm spatial resolution, but also with full hyperspectral information.
The surprising role of the pressure
The new methodology allowed the researchers to better understand the dynamics of the phase transition in VO2. They found that pressure plays a much larger role in light-induced phase transitions than previously expected or assumed.
"We saw that the transient phases aren't nearly as exotic as people had believed! Instead of a truly non-equilibrium phase, what we saw was that we had been misled by the fact that the ultrafast transition intrinsically leads to giant internal pressures in the sample millions of times higher than atmospheric. This pressure changes the material properties and takes time to relax, making it seem like there was a transient phase" says Allan Johnson, postdoctoral researcher at ICFO. "Using our imaging method, we saw that, at least in this case, there was no link between the picosecond dynamics that we did see and any nanoscale changes or exotics phases. So, it looks like some of those conclusions will have to be revisited".
To identify the role played by the pressure in the process, it was crucial to use the hyperspectral image. "By combining imaging and spectroscopy into one great image, we are able to retrieve much more information that permits us to actually see detailed features and decipher exactly where they come from," continues Johnson. "This was essential to look at each part of our crystal and determine whether it was a normal or an exotic out-of-equilibrium phase-and with this information we were able to determine that during the phase transitions all the regions of our crystal were the same, except for the pressure".
Challenging research
One of the main challenges the researchers faced during the experiment was to ensure that the crystal sample of VO2 returned to its original starting phase each time and after being illuminated by the laser. To guarantee that this would occur, they conducted preliminary experiments at synchrotrons where they took several crystal samples and repeatedly shone the laser on them to test their capacity to recover back to their original state.
The second challenge resided in having access to an X-Ray free electron laser, large research facilities where the time windows to conduct the experiments are very competitive and in-demand because there are only a few in the world. "We had to spend two weeks in quarantine in South Korea due to the COVID-19 restrictions before we got our one shot of just five days to make the experiment work, so that was an intense time" Johnson recalls.
Although the researchers describe the present work as fundamental research, the potential applications of this technique could be diverse, since they could “look at polarons moving inside catalytic materials, try imaging superconductivity itself, or even help us understand novel nanotechnologies by viewing and imaging inside nanoscale devices” concludes Johnson.
####
For more information, please click here
Contacts:
Alina Hirschmann
ICFO-The Institute of Photonic Sciences
Cell: 691513974
Copyright © ICFO-The Institute of Photonic Sciences
If you have a comment, please Contact us.Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.
Related Links |
Related News Press |
Quantum Physics
Imaging
The picture of health: Virginia Tech researchers enhance bioimaging and sensing with quantum photonics June 30th, 2023
News and information
New compound unleashes the immune system on metastases September 8th, 2023
Machine learning contributes to better quantum error correction September 8th, 2023
Tests find no free-standing nanotubes released from tire tread wear September 8th, 2023
Quantum chemistry
Quantum materials: Electron spin measured for the first time June 9th, 2023
Quantum communication
IOP Publishing celebrates World Quantum Day with the announcement of a special quantum collection and the winners of two prestigious quantum awards April 14th, 2023
New experiment translates quantum information between technologies in an important step for the quantum internet March 24th, 2023
Researchers demonstrate co-propagation of quantum and classical signals: Study shows that quantum encryption can be implemented in existing fiber networks January 20th, 2023
Videos/Movies
Solvent study solves solar cell durability puzzle: Rice-led project could make perovskite cells ready for prime time September 23rd, 2022
Scientists prepare for the world’s smallest race: Nanocar Race II March 18th, 2022
Visualizing the invisible: New fluorescent DNA label reveals nanoscopic cancer features March 4th, 2022
OCSiAl receives the green light for Luxembourg graphene nanotube facility project to power the next generation of electric vehicles in Europe March 4th, 2022
Possible Futures
New compound unleashes the immune system on metastases September 8th, 2023
Machine learning contributes to better quantum error correction September 8th, 2023
Tests find no free-standing nanotubes released from tire tread wear September 8th, 2023
Chip Technology
University of Chicago scientists invent smallest known way to guide light: 2D optical waveguides could point way to new technology August 11th, 2023
The present and future of computing get a boost from new research July 21st, 2023
Quantum Computing
Training quantum computers: physicists win prestigious IBM Award September 8th, 2023
Machine learning contributes to better quantum error correction September 8th, 2023
Optical computing/Photonic computing
University of Chicago scientists invent smallest known way to guide light: 2D optical waveguides could point way to new technology August 11th, 2023
USTC enhances fluorescence brightness of single silicon carbide spin color centers June 9th, 2023
Discoveries
Electronic detection of DNA nanoballs enables simple pathogen detection Peer-Reviewed Publication September 8th, 2023
Training quantum computers: physicists win prestigious IBM Award September 8th, 2023
Tests find no free-standing nanotubes released from tire tread wear September 8th, 2023
Announcements
Electronic detection of DNA nanoballs enables simple pathogen detection Peer-Reviewed Publication September 8th, 2023
Training quantum computers: physicists win prestigious IBM Award September 8th, 2023
Machine learning contributes to better quantum error correction September 8th, 2023
Tests find no free-standing nanotubes released from tire tread wear September 8th, 2023
Interviews/Book Reviews/Essays/Reports/Podcasts/Journals/White papers/Posters
Electronic detection of DNA nanoballs enables simple pathogen detection Peer-Reviewed Publication September 8th, 2023
New compound unleashes the immune system on metastases September 8th, 2023
Quantum nanoscience
A quantum leap in mechanical oscillator technology August 11th, 2023
Electron collider on a chip June 30th, 2023
![]() |
||
![]() |
||
The latest news from around the world, FREE | ||
![]() |
![]() |
||
Premium Products | ||
![]() |
||
Only the news you want to read!
Learn More |
||
![]() |
||
Full-service, expert consulting
Learn More |
||
![]() |