Resonance-enhanced vibrational spectroscopy of molecules on a superconductor

TL;DR

This paper demonstrates a method to enhance vibrational spectroscopy of molecules on superconductors using Yu-Shiba-Rusinov states, enabling detailed vibrational mode analysis and environmental interaction insights.

Contribution

It introduces a novel approach leveraging YSR states to significantly improve vibrational signal detection in STM spectroscopy of molecules on superconductors.

Findings

Resolved 46 vibrational peaks in a molecule

Achieved energy resolution beyond thermal limits

Used vibrational spectra to study environmental effects on YSR states

Abstract

Molecular vibrational spectroscopy with the scanning tunneling microscope is feasible but usually detects few vibrational modes. We harness sharp Yu-Shiba-Rusinov (YSR) states observed from molecules on a superconductor to significantly enhance the vibrational signal. From a lead phthalocyanin molecule 46 vibrational peaks are resolved enabling a comparison with calculated modes. The energy resolution is improved beyond the thermal broadening limit and shifts induced by neighbor molecules or the position of the microscope tip are determined. Vice versa, spectra of vibrational modes are used to measure the effect of an electrical field on the energy of YSR states. The method may help to further probe the interaction of molecules with their environment and to better understand selection rules for vibrational excitations.