Comment on Recent Tunneling Measurements on Bi-2212

TL;DR

This paper analyzes tunneling conductance asymmetries in Bi-2212, suggesting they indicate a d-wave gap symmetry, and compares this with s-wave symmetries using a detailed tunneling density of states model.

Contribution

It introduces a model for tunneling DOS that incorporates band structure and tunneling directionality to distinguish gap symmetries in Bi-2212.

Findings

Asymmetry in conductance peaks can indicate d-wave gap symmetry.

Switching from d-wave to extended s-wave can reverse conductance asymmetry.

Model differentiates between s-wave and d-wave based on conductance peak behavior.

Abstract

The asymmetry in the conductance peaks shown in recent PCT and STM measurements may be a signature of the d-wave gap. This is based on our model for the tunneling density of states (DOS) which incorporates the group velocity, tunneling directionality, and a realistic band structure. We also make the comparison with the isotropic s-wave and extended s-wave gap symmetries. Whereas the asymmetry of the conductance peaks for the isotropic s-wave tends to reflect the normal state DOS, the asymmetry for the extended s-wave is opposite to that of the d-wave gap. The model shows that a change in the gap symmetry from d-wave to extended s-wave may be accompanied by a switching in the conductance peaks asymmetry.