This award support computational research aimed at understanding the superconducting mechanisms of a class of doped high temperature superconductors, namely the two dimensional compound LiHfNCl and the three dimensional insulator BaKBiO3 that superconduct in the 25-30 K temperature range. Unlike low-temperature heavy fermion superconductors or the high temperature superconducting cuprates and iron pnictides, in which there is strong magnetic behavior near and within the superconducting state and a majority of researchers expect the pairing mechanism to involve magnetism, this class of doped-insulator high temperature superconductors do not contain any magnetic ions, and the electron-phonon coupling is too weak to account for their high critical temperatures.
This project addresses the situation that arises in such materials where a relatively low density of doped carriers interact dynamically within a background of highly charged moving ions. The effective electron-electron interaction is screened both by other electrons and by the moving ions. The conventional means of handling screening, via the random phase approximation, is insufficient, as it misses important short-range correlations resulting from weak short-range screening of strong interactions, and gives an overall weak coupling. The theoretical approach will be to extend the treatment of the dielectric screening matrix beyond the mean field, thereby coupling the screening process of the ions and the carriers. The potential payoff for these investigations is a detailed understanding of a new pairing mechanism that produces superconductivity at 30 K and might be a good candidate to produce substantially higher critical temperatures.
An important outcome of this research that could have a societal impact through sustainable green-energy is the potential discovery and design of new superconductors. This award also supports the education of a graduate student and a postdoctoral research associate at the frontiers of computational condensed matter physics, and will contribute to the training of young scientists who will form tomorrow's scientific and technological workforce.
NONTECHNICAL SUMMARY
This award support computational research aimed at understanding how a class of materials with composition LiHfNCl and BaKBiO3, which do not normally conduct electricity, enter a phase at low temperatures wherein electricity flows through them without any resistance, making them superconductors. Unlike some of the more commonly known superconductors in which the strong interaction of the electrons with the vibrations of the positively charged nuclei are ultimately responsible for their superconducting properties, the electron-nuclei interaction in these materials is not strong enough to account for the observed temperatures at which they become superconducting.
Understanding the newest and most exotic superconductors remains at the intellectual frontier of condensed matter theory. In this project, the PI and his group will develop the theory and perform the necessary large-scale computations to treat dynamical behavior of electrons as they interact with each other and with highly charged moving ions with the ultimate goal of capturing the essential mechanism through which these materials become superconducting.
An important outcome of this research that could have a societal impact through sustainable green-energy is the potential discovery and design of new superconductors. This award also supports the education of a graduate student and a postdoctoral research associate at the frontiers of computational condensed matter physics, and will contribute to the training of young scientists who will form tomorrow's scientific and technological workforce.
