Competing order and the asymmetric tunneling spectrum in high temperature cuprate superconductors

TL;DR

This paper explains the asymmetric tunneling spectrum in cuprate superconductors as a result of competing orders causing charge depletion near the surface, a phenomenon also observed in heavy fermion superconductors.

Contribution

It introduces a general mechanism linking competing orders to tunneling asymmetry, applicable near phase boundaries in correlated electron systems.

Findings

Asymmetric tunneling spectrum explained by competing order effects.

Charge depletion near the surface causes voltage-dependent asymmetry.

Applicable to cuprate and heavy fermion superconductors.

Abstract

We show that the asymmetric tunneling spectrum observed in the cuprate superconductors stems from the existence of a competing order. The competition between the competing order and superconductivity can create a charge depletion region near the surface. The asymmetric response of the depletion region as the function of the external voltage causes the asymmetric tunneling spectrum. The effect is very general in a system which is near the phase boundary of two competing states favoring different carrier densities. The asymmetry which has recently been observed in the point-contact spectroscopy of the heavy fermion superconductor CeCoIn5 is another example of this effect.