Oxides and Chalcogenides - K. Arpino

Topological materials and their protected surface states have deservedly been the subject of intense research, as they provide exciting new theory such as novel states of matter as well as potentially revolutionizing applications such as quantum computing. Thus far, the majority of topology research has focused on heavy-element materials, predominantly intermetallics, and often relied on strong spin-orbit coupling as a critical factor. However, the interactions of bands (a.k.a. chemical bonding), band parity, and structural symmetries also play critical roles in topology.

Our group aims to examine the role that the chemistry of bonding has in topological materials, and how we can use our understanding of that role to direct new research. We place a particular emphasis on the importance of (1) structure and disorder, (2) lone-pair ions as they affect structure & properties, and (3) how the structural chirality may affect chiral states & properties.

The oxides/chalcogenides column of the periodic table provides a range of chemical bonding behaviors, from intermetallic bonding in some tellurides to ionic bonding in some oxides. Specifically, the choice of chalcogen can modulate bond dipole polarity, charge disproportionation, lone-pair stereoactivity & its associated chemical structure, and more. Focusing on this column therefore allows a range of integer compounds as well as the possibility to probe and control the effects of bonding by selective and/or partial ligand substitution. Our work benefits from a collaboration with theorist Maia Garcia Vergniory, whose work (among other things) improves calculations to more accurately capture and predict oxide properties.