Wave-function engineering on superconducting substrates: Chiral Yu-Shiba-Rusinov molecules

TL;DR

This paper demonstrates how magnetic adatoms on superconductors can be engineered to create complex wave-function symmetries, including chiral states, expanding possibilities for topological quantum states.

Contribution

It introduces a method to engineer wave-function symmetries of Yu-Shiba-Rusinov states on superconducting substrates, including the design of chiral wave functions in adatom structures.

Findings

YSR states extend over several nanometers enabling hybridization

Substrate symmetry breaking allows novel wave-function engineering

Chiral wave functions can be designed within adatom structures

Abstract

Magnetic adatoms on superconductors give rise to Yu-Shiba-Rusinov (YSR) states that hold considerable interest for the design of topological superconductivity. Here, we show that YSR states are also an ideal platform to engineer structures with intricate wave-function symmetries. We assemble structures of iron atoms on the quasi-two-dimensional superconductor $2H$-NbSe$_2$. The Yu-Shiba-Rusinov wave functions of individual atoms extend over several nanometers enabling hybridization even at large adatom spacing. We show that the substrate can be exploited to deliberately break symmetries of the adatom structure in ways unachievable in the gas phase. We highlight this potential by designing chiral wave functions of triangular adatom structures confined within a plane. Our results significantly expand the range of interesting quantum states that can be engineered using arrays of magnetic adatoms on superconductors.