Proximity Effect in Normal Metal - High Tc Superconductor Contacts

TL;DR

This paper presents a theoretical study of the proximity effect in normal metal-high Tc superconductor contacts, analyzing how impurity scattering, pairing interactions, and orientation influence local electronic properties and order parameters.

Contribution

It introduces a comprehensive theoretical framework for understanding the proximity effect in d-wave high Tc superconductor contacts, including impurity effects and orientation-dependent order parameter behavior.

Findings

Proximity effect suppresses low-energy density of states in the normal metal.

Induction of a d+is order parameter at [110] interfaces suggests time-reversal symmetry breaking.

Impurity self-energies dominate spectral features over induced pair potentials.

Abstract

We study the proximity effect in good contacts between normal metals and high Tc (d-wave) superconductors. We present theoretical results for the spatially dependent order parameter and local density of states, including effects of impurity scattering in the two sides, s-wave pairing interaction in the normal metal side (attractive or repulsive), as well as subdominant s-wave paring in the superconductor side. For the [100] orientation, a real combination d+s of the order parameters is always found. The spectral signatures of the proximity effect in the normal metal includes a suppression of the low-energy density of states and a finite energy peak structure. These features are mainly due to the impurity self-energies, which dominate over the effects of induced pair potentials. For the [110] orientation, for moderate transparencies, induction of a d+is order parameter on the superconductor side, leads to a proximity induced is order parameter also in the normal metal. The spectral signatures of this type of proximity effect are potentially useful for probing time-reversal symmetry breaking at a [110] interface.