Quasi-particle interference and confinement effects in a correlated Rashba spin-orbit split 2D electron gas

Rashba spin-splitting enables manipulation of spins with electric fields, opening avenues to transformative device concepts. In most materials where Rashba-spin splitting has been observed, the underlying electronic structure is uncorrelated and therefore well described by electronic structure calculations. This is not the case for correlated systems, in which electronic repulsion is needed to be accounted for. Here, we report a scanning tunnelling microscopy, quasiparticle interference (QPI) study of the two-dimensional electron gas (2DEG) at the surface of PdCoO₂, a correlated oxide system reported to exhibit giant Rashba-like spin-splitting [1] Our QPI data reveal a complex quasiparticle scattering pattern which, in particular, consists of a rounded-hexagon shaped, hole-like scattering band that disperses with averaged effective masses of ~ -13.0 m_e and ~ -11.1 m_e along the G-K and G-M directions, respectively. Through comparison with tight-binding calculations, we also show that the scattering is well described once the spin-selection rules are accounted for. Observation of quantized states in a 5-nm wide terrace region confined by a set of parallel step-edges is also discussed.