Structural and electronic properties of ferroelectric domain walls in GeTe from first principles*

Domain walls in ferroelectric oxides can have significantly different properties than their bulk counterparts [1]. This represents a new avenue for the manipulation of material properties for specific purposes. GeTe is a ferroelectric material that is also one of the best performing thermoelectrics, combining beneficial electronic properties with low lattice thermal conductivity [2] and mechanical stability [3]. In this work, we have performed first principles calculations to understand how domain walls affect structural and electronic properties of GeTe. We have identified five different types of domain walls. We find that strong strain-order parameter coupling is present at all of them, which is beneficial for the lattice thermal conductivity reduction. We also show that some of the domain walls are conducting along their planes and insulating out-of-plane. The n- and p-type conduction of these domain walls, discovered in our calculations, presents an opportunity for tuning the electronic transport properties of GeTe for thermoelectric applications.

[1] D. Meier et al, Nat. Mat. 11, 284 (2012)
[2] Z. Liu et al, Proc. Nat. Acad. Sci. USA 115, 5322 (2018)
[3] D. Dangic et al, Phys. Rev. B 97, 224106 (2018)