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Abstract
Topological electronics is a new field that uses topological charges as current-carrying degrees of freedom. For topological electronics applications, systems should host topologically distinct phases to control the topological domain boundary through which the topological charges can flow. Due to their multiple Dirac cones and the π-Berry phase of each Dirac cone, graphene-like electronic structures constitute an ideal platform for topological electronics; graphene can provide various topological phases when incorporated with large spin-orbit coupling and mass-gap tunability via symmetry-breaking. Here, we propose that a (111)-oriented BaBiO3 bilayer (BBL) sandwiched between large-gap perovskite oxides is a promising candidate for topological electronics by realizing a gap-tunable, and consequently a topology-tunable, graphene analogue. Depending on how neighboring perovskite spacers are chosen, the inversion symmetry of the BBL heterostructure can be either conserved or broken, leading to the quantum spin Hall (QSH) and quantum valley Hall (QVH) phases, respectively. BBL sandwiched by ferroelectric compounds enables switching of the QSH and QVH phases and generates the topological domain boundary. Given the abundant order parameters of the sandwiching oxides, the BBL can serve as versatile topological building blocks in oxide heterostructures.
Highlights
The emergence of physical degrees of freedom and their easy manipulation has led to corresponding fields of electronics, such as spintronics[1], valleytronics[2], and plasmonics[3]
The simple design principle applied for construction of the target system is that BaBiO3 bilayer (BBL) provides a graphene-like low-energy electronic degree of freedom, and the sandwiching perovskite oxides, BaMIO3 and BaMIIO3, determine the symmetry of the BBL
If the Bi4+ charge state is unstable in the BBL heterostructure, the quantum spin Hall (QSH) phase seen in the symmetric configuration becomes unstable and transforms into the quantum valley Hall (QVH) phase by spontaneously breaking the sublattice symmetry
Summary
The emergence of physical degrees of freedom and their easy manipulation has led to corresponding fields of electronics, such as spintronics[1], valleytronics[2], and plasmonics[3]. Whereby information is carried by the topological charge through the topological domain boundary[5,6], at least two distinct topological phases should be accessible and controllable within a system. In this regard, a gap-tunable graphene-like electronic structure[7,8] is an ideal candidate for topological electronics applications. The maximum band-gap tunability of a Dirac cone, which is essential for topological electronics but barely achievable in graphene[12], can be realized in a (111)-oriented BaBiO3 bilayer (BBL) oxide heterostructure. The abundant order parameters of the sandwiching oxide perovskite materials can break various symmetries of BBL, allowing it to possess various topological phases
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