Abstract
Exploiting inversion symmetry breaking (ISB) in systems with strong spin-orbit coupling promises control of spin through electric fields-crucial to achieve miniaturization in spintronic devices. Delivering on this promise requires a two-dimensional electron gas with a spin precession length shorter than the spin coherence length and a large spin splitting so that spin manipulation can be achieved over length scales of nanometers. Recently, the transition metal oxide terminations of delafossite oxides were found to exhibit a large Rashba spin splitting dominated by ISB. In this limit, the Fermi surface exhibits the same spin texture as for weak ISB, but the orbital texture is completely different, raising questions about the effect on quasiparticle scattering. We demonstrate that the spin-orbital selection rules relevant for conventional Rashba system are obeyed as true spin selection rules in this correlated electron liquid and determine its spin coherence length from quasiparticle interference imaging.
Highlights
Spin-orbit coupling (SOC) in combination with inversion symmetry breaking (ISB) leads to the lifting of spin degeneracy [1, 2] and promises spin manipulation without the need for magnetic fields
The Rashba physics seen in the delafossites arises because the unusual orientation of the transition metal octahedra in the delafossite structure leads to extremely large energy scales for the ISB [6]
The standard cases of large Rashba splitting, the observed effect is limited by the ISB energy scale, which is a weak perturbation compared to the atomic SOC energy scale
Summary
Spin-orbit coupling (SOC) in combination with inversion symmetry breaking (ISB) leads to the lifting of spin degeneracy [1, 2] and promises spin manipulation without the need for magnetic fields. The delafossite metals [7,8,9] grow with astonishing crystalline purity [10] and show extremely long mean free paths as evidenced by bulk transport [11], transverse electron focusing [12], and even coherent Aharonov-Bohm–like oscillations [13] They have been shown to have surface states with very large Rashba splitting (∼70 meV and ∼150 meV in PdCoO2 and PdRhO2, respectively). In the standard cases of large Rashba splitting, the observed effect is limited by the ISB energy scale, which is a weak perturbation compared to the atomic SOC energy scale In the delafossites, it is not, so the full bare atomic SOC determines the splitting, leading to a giant spin splitting in a materials system composed of comparatively light elements
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