Members from the Zou and Damascelli groups visited the Diamond Light Source (DLS) at Oxford, UK, July 16-19, the first visit to the facilities by QMI members.
Ryan Day, Fengmiao Li, and Chong Liu had their application for beamtime at the world-renowned synchrotron facility accepted, allowing them to perform measurements on monolayer FeSe samples, a unique and interesting Fe-based superconductor grown at QMI. There are only 70 synchrotrons in the world, and the DLS is among the few capable of producing the desired intensity of light and providing the required facilities for angle-resolved photo emission spectroscopy (ARPES). Previously, similar measurements have been carried out at Brookhaven National Laboratory in New York.
Aside from the 8-hour time difference, one of the biggest challenges of conducting ARPES experiments at an offsite facility like the DLS, is to transport these delicate samples to the synchrotrons while maintaining their delicate electronic surface states. ARPES measurements require the sample surfaces to be in perfect condition and atomically clean. Whereas bulk materials can be cleaved in situ in ultra-high vacuum, thus ensuring a pristine sample surface, thin film samples have to go through a process of “capping and decapping,” requiring an additional protective layer of materials to be grown and later removed.
Next steps will focus on further experiments and improved methods for transporting thin film samples to offsite characterization tools. QMI has recently purchased an ultra-high-vacuum suitcase for this purpose.
“In order to get this project to a state of completion, further experiments will be essential, and we intend to carry these out at the beginning of December at the new QMSC (Quantum Materials Spectroscopy Centre) beamline at the Canadian Light Source in Saskatoon,” explains Ryan Day. “We are also currently developing our own decapping facility where high temperatures and very low pressures will be possible, allowing us to prepare a cleaner sample for measurements. This project was one of the final projects worked on by the Quantum Pathways students this summer. Perhaps more importantly, the QMSC at the Canadian Light Source can provide photon energies down to much lower levels than either Brookhaven or Diamond could provide, at very high intensities. This will make a huge difference, and we are very excited to continue these experiments towards a successful completion later this fall.
"The exciting results we collected at Diamond were captured on the very edge of the range of photon energies the ARPES beamline at Diamond can provide."
Story: Ryan Day, Sophia Han, Ke Zou
Photo: Pinder Dosanjh
Ke Zou, Chong Liu, Ryan Day, DLS staff member, and Fengmiao Li onsite at the DLS