Topological States in Dimerized Quantum-Dot Chains Created by Atom Manipulation

TL;DR

This study demonstrates the creation of one-dimensional topological phases in dimerized quantum-dot chains assembled with atomic precision, revealing boundary states and the influence of electrostatics, with implications for engineered quantum materials.

Contribution

It introduces a method to create and control topological states in quantum-dot chains using atom manipulation and electrostatic gating, advancing quantum engineering techniques.

Findings

End states consistent with SSH model observed

Electrostatic potential causes asymmetry in energy spectrum

Gating enables control over boundary state superpositions

Abstract

Topological electronic phases exist in a variety of naturally occurring materials but can also be created artificially. We used a cryogenic scanning tunneling microscope to create dimerized chains of identical quantum dots on a semiconductor surface and to demonstrate that these chains give rise to one-dimensional topological phases. The dots were assembled from charged adatoms, creating a confining potential with single-atom precision acting on electrons in surface states of the semiconductor. Quantum coupling between the dots leads to electronic states localized at the ends of the chains, as well as at deliberately created internal domain walls, in agreement with the predictions of the Su-Schrieffer-Heeger model. Scanning tunneling spectroscopy also reveals deviations from this well-established model manifested in an asymmetric level spectrum and energy shifts of the boundary states. The deviations arise because the dots are charged and hence lead to an onsite potential that varies along the chain. We show that this variation can be mitigated by electrostatic gating using auxiliary charged adatoms, enabling fine-tuning of the boundary states and control of their quantum superposition. The experimental data, which are complemented by theoretical modeling of the potential and the resulting eigenstates, reveal the important role of electrostatics in these engineered quantum structures.