Creating tunable and coupled Rashba-type quantum dots atom-by-atom

TL;DR

This paper demonstrates the creation and analysis of tunable, coupled quantum dots on a Rashba surface alloy, revealing complex electronic behaviors influenced by spin-orbit coupling and quantum confinement.

Contribution

It introduces a method to fabricate and study coupled quantum dots on a Rashba surface alloy, highlighting anisotropic coupling effects and potential for topological artificial lattices.

Findings

Quantum dots exhibit complex density of states patterns.

Coupling between dots is anisotropic and tunable.

Spin-orbit coupling influences quantum confinement and scattering.

Abstract

Artificial lattices created by assembling atoms on a surface with scanning tunneling microscopy present a platform to create matter with tailored electronic, magnetic and topological properties. However, such artificial lattices studies to date have focused exclusively on surfaces with weak spin-orbit coupling. Here, we created artificial and coupled quantum dots by fabricating quantum corrals from iron atoms on the prototypical Rashba surface alloy, BiCu2, using low-temperature scanning tunneling microscopy. We quantified the quantum confinement of such quantum dots with various diameter and related this to the spatially dependent density of states, using scanning tunneling spectroscopy. We found that the density of states shows complex distributions beyond the typical isotropic patterns seen in radially symmetric structures on (111) noble metal surfaces. We related these to the energy-dependent interplay of the confinement potential with the hexagonal warping and multiple intra- and interband scattering vectors, which we simulated with a particle-in-a-box model that considers the Rashba-type band structure of BiCu2. Based on these results, we studied the effect of coupling two quantum dots and exploited the resultant anisotropic coupling derived from the symmetry of the various scattering channels. The large anisotropy and spin-orbit coupling provided by the BiCu2 platform are two key ingredients toward creation of correlated artificial lattices with non-trivial topology.