Maximal Rashba-like spin splitting via kinetic energy-driven inversion symmetry breaking

TL;DR

This paper introduces a kinetic energy-driven mechanism for large inversion symmetry breaking at surfaces, leading to significant Rashba-like spin splittings in transition-metal oxides, with implications for oxide spintronics.

Contribution

It uncovers a new kinetic energy-driven mechanism for large inversion symmetry breaking, enabling enhanced Rashba-like spin splittings in oxides.

Findings

Surface states of transition-metal oxides exhibit large Rashba-like spin splittings.

The mechanism is based on asymmetry of surface hopping energies.

Potential for designing oxide-based spintronic devices.

Abstract

Engineering and enhancing inversion symmetry breaking in solids is a major goal in condensed matter physics and materials science, as a route to advancing new physics and applications ranging from improved ferroelectrics for memory devices to materials hosting Majorana zero modes for quantum computing. Here, we uncover a new mechanism for realising a much larger energy scale of inversion symmetry breaking at surfaces and interfaces than is typically achieved. The key ingredient is a pronounced asymmetry of surface hopping energies, i.e. a kinetic energy-driven inversion symmetry breaking, whose energy scale is pinned at a significant fraction of the bandwidth. We show, from spin- and angle-resolved photoemission, how this enables surface states of 3d and 4d-based transition-metal oxides to surprisingly develop some of the largest Rashba-like spin splittings that are known. Our findings open new possibilities to produce spin textured states in oxides which exploit the full potential of the bare atomic spin-orbit coupling, raising exciting prospects for oxide spintronics. More generally, the core structural building blocks which enable this are common to numerous materials, providing the prospect of enhanced inversion symmetry breaking at judiciously-chosen surfaces of a plethora of compounds, and suggesting routes to interfacial control of inversion symmetry breaking in designer heterostructures.