Strongly enhanced Rashba splittings in oxide heterostructure: a tantalite monolayer on BaHfO$_3$

TL;DR

This paper proposes a heterostructure of tantalate monolayer on BaHfO3 that exhibits significantly enhanced Rashba spin splitting, potentially enabling new topological and correlated electronic phenomena.

Contribution

It demonstrates, through first-principles calculations and modeling, that a tantalate monolayer on BaHfO3 can achieve large Rashba splitting, advancing the design of oxide heterostructures for exotic quantum states.

Findings

Rashba splitting up to nearly 10% of bandwidth observed.

Tantalate monolayer on BaHfO3 hosts 2D bands with strong spin-orbit coupling.

The structure is promising for topological superconductivity and Majorana fermions.

Abstract

In the two-dimensional electron gas (2DEG) emerging at the transition metal oxide surface and interface, it has been pointed out that the Rashba spin-orbit interaction, the momentum-dependent spin splitting due to broken inversion symmetry and atomic spin-orbit coupling, can have profound effects on electronic ordering in the spin, orbit, and charge channels, and may help give rise to exotic phenomena such as ferromagnetism-superconductivity coexistence and topological superconductivity. Although a large Rashba splitting is expected to improve experimental accessibility of such phenomena, it has not been understood how we can maximally enhance this splitting. Here, we present a promising route to realize significant Rashba-type band splitting using a thin film heterostructure. Based on first-principles methods and analytic model analyses, a tantalate monolayer on BaHfO$_3$ is shown to host two-dimensional bands originating from Ta $t_{2g}$ states with strong Rashba spin splittings - up to nearly 10% of the bandwidth - at both the band minima and saddle points due to the maximal breaking of the inversion symmetry. Such 2DEG band structure makes this oxide heterostructure a promising platform for realizing both a topological superconductor which hosts Majorana fermions and the electron correlation physics with strong spin-orbit coupling.