Nanoscale Control of Quantum States in Radical Molecules on Superconducting Pb(111)

TL;DR

This study demonstrates precise control and manipulation of quantum states in radical molecules on a superconducting surface, enabling quantum-state engineering through molecular assembly and tip positioning.

Contribution

It introduces a method to manipulate magnetic and quantum states of radical molecules on superconductors using scanning tunneling microscopy, revealing controllable Yu-Shiba-Rusinov states and molecular chain configurations.

Findings

Quantum phase transition from singlet to doublet states induced by tip distance.

Tuning of YSR states by altering molecular arrangements and orientations.

Construction of molecular chains with switchable dimer configurations for information encoding.

Abstract

Magnetic impurities on superconductors present a viable platform for building advanced applications in quantum technologies. However, a controlled manipulation of their quantum states continues to pose a significant challenge, hindering the progress in the field. Here we show the manipulation of magnetic states in the radical molecule 4,5,9,10-tetrabromo-1,3,6,8-tetraazapyrene (TBTAP) on a Pb(111) superconducting surface using low-temperature scanning tunneling microscopy. Tunneling spectra reveal Yu-Shiba-Rusinov (YSR) states near the Fermi energy in isolated molecules. A quantum phase transition from singlet to doublet ground state is induced by changing the tip-molecule distance. Additionally, the presence of a second TBTAP molecule allows tuning of the YSR state position by altering the relative distance and can induce splitting of the YSR states for certain orientations. The construction of molecular chains up to pentamers shows periodic arrangements of charged and neutral molecules, with even-numbered chains forming a charged dimer structure at one end. Information can be encoded in these chains by switching the dimer position. These findings elucidate interactions between molecular assemblies and superconducting substrates, paving the way for advanced quantum-state engineering.