Mar 5 2019
Mott insulators are odd materials. They should conduct electricity under normal electron band theory; however, they do not do so because of the interactions among their electrons.
Schematic of eta-pairing (Image credit: RIKEN)
Yet, researchers from the RIKEN Cluster for Pioneering Research have now demonstrated that light pulses can possibly be used for converting these materials beyond basic conductors to superconductors. Superconductors are a special class of materials that conduct electricity without any loss in energy. Such a process would occur via an unusual type of superconductivity called “eta pairing.”
The researchers used numerical simulations and eventually discovered that this unusual type of conductivity, which is assumed to occur under non-equilibrium conditions in robustly correlated materials like iron-pnictides and high-Tc cuprates, emerges owing to a phenomenon called eta pairing. This phenomenon is different from the superconductivity seen in the same robustly correlated materials under equilibrium circumstances, and is believed to involve repulsive interactions between specific electrons inside the structure. It is equally different from conventional superconductivity, in which the phenomenon occurs because of the interactions between the vibrations of the crystal structure and the electrons, causing mutual interactions between the electrons via vibrations and therefore, overcoming the repulsion existing between the electrons.
Three decades ago, Chen-Ning, a mathematical physicist, originally suggested the concept of eta-pairing; however, as it was a purely mathematical concept, it was inferred as a virtual phenomenon that would not occur in the real world.
Yet, for the current research, non-equilibrium dynamics was used by the team to examine the impact of light pulses on a Mott insulator, and observed that the impact would actually occur in the real world.
What is interesting is that our calculations showed that this takes place based on the beautiful mathematical structure that Yang and his followers formulated so many years ago.
Tatsuya Kaneko, Study First Author and Postdoctoral Researcher, RIKEN Cluster for Pioneering Research
This work provides new insights not only into the phenomenon of non-equilibrium dynamics, but also could lead to the development of new high-temperature superconductors, which could be useful in applications. What remains is to perform actual experiments with Mott insulators to verify that this process actually takes place.
Seiji Yunoki, Study Lead, RIKEN
The study has been published in Physical Review Letters.