Comment on `Anomalously Large Gap Anisotropy in the a-b Plane of Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$'

TL;DR

This comment critiques the interpretation of ARPES data suggesting d_{x^{2}-y^{2}} pairing symmetry in Bi-2212, highlighting ambiguities and the possibility of d_{xy} pairing symmetry.

Contribution

It challenges previous conclusions about pairing symmetry in Bi-2212 by analyzing ARPES data interpretation ambiguities.

Findings

The interpretation of ARPES edge shifts is not unambiguous.

d_{xy} pairing symmetry cannot be ruled out based on current data.

The original interpretation may overlook alternative pairing symmetries.

Abstract

Comment on `Anomalously Large Gap Anisotropy in the a-b Plane of Bi$_{{\bf 2}}$Sr$_{{\bf 2}}$CaCu$_{{\bf 2}}$O$_{{\bf 8+}{\delta}}$', Kazumasa Miyake and Osamu Narikiyo, In a recent Letter, Shen and collaborators [Phys. Rev. Lett. {\bf 70}, 1555 (1993)] reported that angle-resolved photoemission spectra (ARPES) in Bi-2212 cuprate superconductor far below $T_{{\rm c}}$ has anomalously large anisotropy and then concluded that the symmetry of Cooper pair is likely to be $d_{x^{2}-y^{2}}$, i.e., $\Delta_{{\bf k}}=\Delta(\cos k_{x}a-\cos k_{y}a)$. In this Comment we point out that the interpretation done by Shen {\it et al\/.}, where the shift of edge near Fermi level has been identified with the gap $\Delta_{{\bf k}}$, is not unambiguous, and that a possibility of $d_{xy}$ pairing, i.e., $\Delta_{{\bf k}}=2\Delta\sin k_{x}a\sin k_{y}a$, cannot be ruled out.