Theory + MBE + ARPES to navigate correlated materials
How are materials discovered?
Theorists can guide the creation of artificial quantum materials as long as “conventional” building blocks are used. Once strong inter- actions between the building blocks play a role, new parameters are required to successfully predict the materials’ properties.PARADIM’s in-house research team is exploiting the world-leading tools of its Platform to provide a new modality of materials discovery for artificial quantum materials. This occurs through the unique combination of thin film growth with in- situ spectroscopy enabling scientists to directly see the impact of changes in structure on how the electrons move in these materials. Although calculating this behavior directly for this class of materials is beyond current theories, the resulting behavior can be fit by theory and used to more accurately guide materials discovery.
Closing the materials-by-design loop has enabled PARADIM scientists to predict and demonstrate the behavior of the superconductor Sr2RuO4 under strain.
A recent publication showcased the benefits of MBE+ARPES for the creation and understanding of artificial quantum materials . Contemporary materials-by-design involves “conventional” materials, where first principles density functional calculations employing the local density approximation work reasonably well because electron exchange and correlation effects are minimal. But what about those materials for which it does not, i.e., the subset of quantum materials in which electron exchange and correlation effects are significant? Discoveries in such important materials have historically been driven by experimental discovery with little or no theoretical guidance.
PARADIM’s combination of oxide MBE with ARPES enables the integrated materials-by-design discovery loop for artificial quantum materials shown above. With its direct, ultra-high vacuum connection between MBE and ARPES systems, PARADIM makes it possible to measure the electronic structure of quantum materials and then subject them to systematic changes in strain, doping, cation ordering, dimensional confinement, or other perturbations to the structure and see how the electronic structure evolves. This is an ideal situation for theorists working on quantum materials as they can see the effects of adjusting specific control parameters on electronic structure and with that input refine their theoretical methods to better describe these materials. Further, this approach frees ARPES of its traditional limitation of only being applicable to materials that (1) can be prepared as single crystals and (2) cleave. An example of this loop in action is the MBE+ARPES measurements of the electronic structure of Sr2RuO4 films as a function of biaxial strain. Fitting the observed electronic structure and its evolution to various theoretical models has allowed PARADIM theorists  and others  to predict how to increase the superconducting transition temperature of Sr2RuO4 films while maintaining the desired odd parity spin triplet pairing of this unusual superconductor.
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