Polar metals

A polar metal is a material that can conduct electrons and also contain internal electric dipole moments. The coexistence of metallicity and electric dipoles is rather unusual, as conduction electrons screen internal dipole moments.

The concept of a polar metal is not a new one. Anderson and Blount [1] first came up with the idea in 1964. It took almost 50 years for this prediction to bear fruits in the lab, and in 2013 the first definitive polar metal, LiOsO3, was discovered. In this material, the Li atoms are solely responsible for the polar distortion, while the Os atoms participate in the conduction. It is this very decoupling of the structural and electronic degrees of freedom that allow for the polar metallic state. In my research I am exploring how this coupling can be manipulated and the subsequent effects on the electronic structure.

Polar metallicity is distinct from ferroelectricity, as the polarisation in a polar metal is not required to be switchable, as is the case for a ferroelectric. For practical considerations, ferroelectricity is foundational to many so-called "Beyond Moore's Law" electronics, and so a theory for switchable polar metals is an outstanding question.

In the video below I use Density Functional Theory to understand the effect of strain on the polar metal LiOsO3.

References

[1]: Anderson, P. W.; Blount, E. I. (15 February 1965). "Symmetry Considerations on Martensitic Transformations: "Ferroelectric" Metals?". Physical Review Letters. 14 (7): 217–219. https://doi.org/10.1103/PhysRevLett.14.217.

[2]: Shi, Y., Guo, Y., Wang, X. et al. A ferroelectric-like structural transition in a metal. Nature Mater 12, 1024–1027 (2013). https://doi.org/10.1038/nmat3754.