Theory of point contact spectroscopy in electron-doped cuprates

TL;DR

This paper explains why zero bias conductance peaks are rarely observed in electron-doped cuprates by showing that antiferromagnetic order suppresses midgap surface states, aligning theoretical calculations with experimental results.

Contribution

It generalizes the BTK formula to include antiferromagnetic coupling, revealing how AF order destroys midgap surface states in electron-doped cuprates.

Findings

AF order suppresses midgap surface states

Calculated PCS matches experimental observations

ZBCP is absent due to AF and SC coexistence

Abstract

In the hole-doped $d_{x^{2}-y^{2}}$-wave cuprate superconductor, due to the midgap surface state (MSS), a zero bias conductance peak (ZBCP) is widely observed in [110] interface point contact spectroscopy (PCS). However, ZBCP of this geometry is rarely observed in the electron-doped cuprates, even though their pairing symmetry is still likely the $d_{x^{2}-y^{2}}$-wave. We argue that this is due to the coexistence of antiferromagnetic (AF) and the superconducting (SC) orders. Generalizing the Blonder-Tinkham-Klapwijk (BTK) formula to include an AF coupling, it is shown explicitly that the MSS is destroyed by the AF order. The calculated PCS is in good agreement with the experiments.