From sustainable energy to quantum computers: high-temperature superconductors have the potential to revolutionize modern technology.
Higgs spectroscopy can cause water absorption areas because it shows the dynamics of electron pairs in superconductors.
It is noteworthy that dynamics also exhibit typical precursors for superconductivity, even above the critical temperature at which the material under investigation reaches superconductivity.
Superconductors transport electricity without losing energy. Using it can dramatically reduce our energy needs – unless superconductivity requires temperatures of -140 degrees Celsius and below. Materials only “include” their superconductivity below this point.
Higgs spectroscopy allows new insights into high-temperature superconductivity
“Higgs spectroscopy offers us an entirely new magnifying glass to examine physical processes,” Dr. Jan-Christoph Dainer.
Researchers at the Radiation Physics Institute at HZDR are working on new methods together with colleagues from MPI-FKF, universities in Stuttgart and Tokyo and other international research institutes.
Scientists want to find out how electrons form pairs in high-temperature superconductors.
In superconductivity, electrons combine to form Cooper pairs so that they can move through paired matter without interacting with the medium.
There is a physical explanation for conventional superconductors: “Electrons are paired due to crystal lattice vibrations,” explained Prof. Stefan Kaiser, one of the main authors of this research, who studies superconductor dynamics at MPI-FKF and Stuttgart University.
“One hypothesis is that this pair is caused by fluctuating rotations, namely magnetic interactions,” Kaiser explained. “But the key question is: Can it directly affect superconductivity and, in particular, the properties of Cooper pairs be measured?”
However, such a single pulse is not enough for high-temperature superconductors, because the system is too much damped by interactions between superconductors and non-conductor conductors and complex symmetry of stacking parameters.
The terahertz light source keeps the system vibrating
Thanks to the Higgs spectroscopy, a research consortium led by MPI-FKF and HZDR achieved an experimental breakthrough for high-temperature superconductors.
The trick is to use a very strong, multicyclic terahertz pulse that optimally matches the Higgs vibration and can withstand it despite damping factors – which continually create a metaphorical pendulum.
With a highly efficient terahertz light source, TELBE at HZDR, the researchers can send 100,000 pulses per second through samples.
“Our source is unique in the world because of its high intensity in the terahertz range, combined with a very high repetition rate,” explained Dainer. “We can now selectively control the Higgs vibrations and measure them.”
“Experiments are very important for scientific applications from large research institutions in general. They show that high-performance terachet sources such as TELBE can conduct complex research using nonlinear terahertz spectroscopy on complex sample sets, for example cuprate.”
For this reason, the research team expects high demand in the future: “Higgs spectroscopy as a methodical approach opens up entirely new possibilities,” explained Dr. Hao Chu, lead author of the study and postdoctoral colleague at UBC Max Planck UTokyo Center for Quantum Materials.
“This is the starting point for a series of experiments that provide new insights about these complex materials. Now we can take a very systematic approach.”
By doing a series of measurements, the researchers were initially able to show that their method worked for typical cuprates. Under the critical temperature, the research team not only succeeded in stimulating the Higgs vibration, but also to prove that the new excitation unconsciously interacts with the Higgs vibration from the Cooper pair.
In addition, the researchers saw evidence that the Cooper pair could form above critical temperatures, though without hesitation. Other previous measurement methods suggest the possibility of the initial installation.
Higgs spectroscopy can support this hypothesis and explain when and how pairs are formed and why they vibrate together in superconductors.
Reference: H. Chu, M.-J. Kim, K. Katsumi, S. Kovalev, R. D. Dawson, L. Schwarz, N. Yoshikawa, G. Kim, D. Putzky, Z. Z. Li, H. Raffy, S. Germanskiy, J.-C. Deinert, N. Awari, I. Ilyakov, B. Green, M. Chen, M. Bawatna, G. Cristiani, G. Logvenov, Y. Gallais, A. V. Boris, B. Keimer, A. P. Schnyder, D. Manske, M. Gensch, Z. Wang, R. Shimano, S. Kaiser: Phase-resolved Higgs response in superconducting cuprates, in Nature Communications, 2020 (DOI: 10.1038/s41467-020-15613-1)