Hydrogen Bonding and Symmetry Relationships in FeSe-based superconductors

Monday, November 4, 2019 - 4:00pm

I will present our work on iron-based superconductors where hydrogen bonding plays a role in stabilizing structures that would otherwise not exist. In this lecture I will focus on the layered iron-based superconductors and the intercalated phases such as (Li1-xFexOH)FeCh, [Na1-xFex(OH)2]FeCh, and [Li(C2H8N2)y]FeCh where Ch is S and Se. New physics can be uncovered through such synthetic methods since it can for example place a ferrimagnetic layer proximate to a superconducting layer as in (Li1-xFexOH)FeS.  We propose that hydrogen bonding of the type N—H···Ch and O—H···Ch stabilize the growth of these layered iron chalcogenides. Due to the preparation from hydrothermal and solvothermal syntheses, the crystal growth of these layers involves several intermediate phases involving hydrogen bonding as evidenced by in situ X-ray diffraction studies. Finally, I will discuss some chemical bonding concepts that arise from group-subgroup relationships during phase transitions in these materials. It is clear that these layered chalcogenides support square lattices where electronic instabilities give way to either bonding distortions or superconductivity. 

Prof. Efrain Rodriguez - U. Maryland
Deepak Singh