Topological soliton molecule in quasi 1D charge density wave

TL;DR

This paper reports the first observation of a topological soliton molecule in a quasi 1D charge density wave system, revealing bound states of solitons with potential for advanced electronic states and data storage.

Contribution

It demonstrates the formation of a topological soliton molecule in an electronic system, combining experimental STM evidence with theoretical DFT analysis.

Findings

Identification of a bound state of right- and left-chiral solitons

Observation of in-gap states and zero phase shift

Theoretical evidence of attractive soliton interactions

Abstract

Soliton molecules, bound states of two solitons, can be important for the informatics using solitons and the quest for exotic particles in a wide range of physical systems from unconventional superconductors to nuclear matter and Higgs field, but have been observed only in temporal dimension for classical wave optical systems. Here, we identify a topological soliton molecule formed spatially in an electronic system, a quasi 1D charge density wave of indium atomic wires. This system is composed of two coupled Peierls chains, which are endowed with a Z$_4$ topology and three distinct, right-chiral, left-chiral, and non-chiral, solitons. Our scanning tunneling microscopy measurements identify a bound state of right- and left-chiral solitons with distinct in-gap states and net zero phase shift. Our density functional theory calculations reveal the attractive interaction of these solitons and the hybridization of their electronic states. This result initiates the study of the interaction between solitons in electronic systems, which can provide novel manybody electronic states and extra data-handling capacity beyond the given soliton topology.