Quartett formation at (100)/(110)-interfaces of d-wave superconductors

TL;DR

This paper models the formation of quartett states at (100)/(110) interfaces of d-wave superconductors, revealing how attractive interactions promote boson binding and relate to observed h/4e oscillations in cuprate SQUIDs.

Contribution

It introduces a one-dimensional boson lattice model to explain quartett formation at superconductor interfaces, linking microscopic interactions to experimental oscillation phenomena.

Findings

Attractive boson interactions enhance quartett binding at interfaces.

The model explains h/4e oscillations observed in cuprate SQUIDs.

Alternating sign of Josephson coupling influences quartett formation.

Abstract

Across a faceted (100)/(110) interface between two d-wave-superconductors the structure of the superconducting order parameter leads to an alternating sign of the local Josephson coupling. Describing the Cooper pair motion along and across the interface by a one-dimensional boson lattice model, we show that a small attractive interaction between the bosons boosts boson binding at the interface -- a phenomenon, which is intimately tied to the staggered sequence of 0- and Pi-junction contacts along the interface. We connect this finding to the recently observed h/4e oscillations in (100)/(110) SQUIDS of cuprate superconductors.