Role of magnetism and electron-lattice interactions in STM spectra of cuprates

TL;DR

This paper reanalyzes STM data on cuprates, suggesting the observed bosonic mode is likely due to magnetic excitations rather than lattice phonons, challenging previous interpretations of the mode’s role in superconductivity.

Contribution

It provides a reinterpretation of STM spectra, arguing that magnetic excitations, not phonons, are responsible for the observed bosonic mode in cuprates.

Findings

The observed mode is consistent with magnetic excitations.

The lattice mode is likely due to inelastic tunneling, not phonons.

Magnetic excitations are more relevant to superconductivity in cuprates.

Abstract

The study of bosonic modes that couple to the charge carriers is a key element in understanding superconductivity. Lee et al. have used atomic-resolution scanning tunneling spectroscopy (STM) in an attempt to extract the spectrum of of these modes in the high temperature superconductor Bi2Sr2CaCu2O8+d and they found a mode whose frequency did not depend on doping but changed on 16O to 18O isotopic substitution leading them to suggest a role for lattice modes (phonons). A careful examination of their published data reveals a weaker but distinct feature that has all the characteristics of the magnetic excitation identified as the bosonic mode in other competing experiments. We suggest the lattice mode seen by Lee et al. is not relevant to superconductivity and is due to inelastic tunneling through the insulating oxide layer.