Artificial oxide heterostructures with non-trivial topology

Area of Science:

• Condensed Matter Physics
• Materials Science
• Solid-State Physics

Background:

• Topological insulators with large band gaps are crucial for next-generation electronics.
• Rashba spin-orbit interactions in heterostructures are key to achieving large band gaps.
• Transition metal oxides containing heavy ions are promising candidates for such materials.

Purpose of the Study:

• To explore design principles for stacking oxide Rashba layers for topological insulator applications.
• To investigate the creation of 2D and 3D topological insulating phases through controlled stacking.
• To classify the resulting topological phases and identify mechanisms for isolating topological states.

Main Methods:

• Theoretical discussion of heterostructure design principles.
• Modeling of stacked layers with two-dimensional electron gases (2DEGs).
• Analysis of coupling strengths (intra- and interlayer) and their effect on topological phases.
• Investigation of symmetry protection and momentum-dependent coupling terms.

Main Results:

• A 2D topological insulating phase emerges with negative coupling between 2DEGs in a single building block.
• Stacking multiple blocks allows artificial creation of 2D or 3D topological insulators.
• The 3D topological insulator is protected by reflection symmetry, classifying it as a topological crystalline insulator.
• Quadratic momentum-dependent intralayer coupling is proposed to isolate topological states, achievable via layer buckling.

Conclusions:

• Stacked oxide Rashba systems offer a viable route to engineered topological insulators.
• Layer buckling is a potential mechanism to realize necessary coupling for topological states.
• This approach aligns with alternative methods for creating topological phases in perovskite oxides.