On the Origin of the Tunneling Asymmetry in the Cuprate Superconductors

TL;DR

This paper explains the tunneling asymmetry in cuprate superconductors as arising from incoherent spectral weight, revealing a new energy scale related to spin-charge recombination through analysis of STM data.

Contribution

It introduces a novel interpretation of tunneling asymmetry as due to incoherent spectral parts and identifies a potential new energy scale in cuprates.

Findings

Incoherent spectral weight causes tunneling asymmetry.

A well-defined gap of 25 meV is observed in the difference spectrum.

This gap may indicate the energy scale for spin-charge recombination.

Abstract

We argue the coherent part of the spectral weight always contribute symmetrically to the STM spectrum at sufficiently low energy and the tunneling asymmetry is a manifestation of the incoherent part of the electron spectrum. By subtracting the particle side spectrum from the hole side spectrum in the published STM data of Pan \textit{et al} on $BSCCO_{2212}(T_{c}=84K)$, we find the difference spectrum show a well defined gap structure at 25 meV. We argue this gap may represent a new energy scale of the system, namely the energy scale for spin-charge recombination in this system.