Role of Inelastic Tunneling through the Barrier in Scanning Tunneling Microscope Experiments on Cuprates

TL;DR

This paper investigates how inelastic tunneling processes through oxide barriers influence scanning tunneling spectra in cuprate superconductors, highlighting phonon contributions and aligning theoretical calculations with experimental data.

Contribution

It introduces a model for inelastic tunneling via apical O-phonons in cuprates, explaining spectral features observed in experiments and proposing tests to distinguish phonon types.

Findings

Inelastic processes cause peaks in second derivative spectra displaced by phonon energies.

Calculations with apical O-phonons match experimental spectral features.

Proposed tests can differentiate between apical and planar phonon contributions.

Abstract

The tunneling path between the CuO2-layers in cuprate superconductors and a scanning tunneling microscope tip passes through a barrier made from other oxide layers. This opens up the possibility that inelastic processes in the barrier contribute to the tunneling spectra. Such processes cause one or possibly more peaks in the second derivative current-voltage spectra displaced by phonon energies from the density of states singularity associated with superconductivity. Calculations of inelastic processes generated by apical O-phonons show good qualitative agreement with recent experiments reported by Lee et al.[1]. Further tests to discriminate between these inelastic processes and coupling to planar phonons are proposed.