Heterostructures*

Domain walls that form between tetragonal domains in SrTiO₃ (STO) at low temperatures have been shown to host a number of interesting phenomenon including polar order¹, magnetism², and preferred conductivity³. They also contribute to unexpected transport behaviors in the two-dimensional carrier gas (2DCG) formed at the interface of STO surfaces and interfaces. Here we discuss our recent findings of a finite transverse resistance in zero field, in the 2DCG between amorphous aluminum oxide (AlO_x) and (001) and (111) oriented STO substrates. The effect first arises at temperatures ~70 K but is most prominent around ~40 K, the temperature at which the domain walls become increasingly polar. We argue that the preferential transport of current along polar domain walls can explain the finite transverse resistance. Surprisingly, the effect is stronger in (111) oriented devices than in (001) oriented devices. This difference is correlated with a difference in the dielectric constant between the (001) and (111) oriented substrates at low temperatures.

[1] Scott et al., PRL 109, 187601 (2012)
[2] Christensen et al., Nat. Phys. 15, 269 (2019).
[3] Kalisky et al., Nat. Mat. 12, 1091 (2013).