hc/4e oscillations in a model for (100)/(110) SQUIDs of d-wave superconductors

TL;DR

This paper models a SQUID with d-wave superconductors to predict hc/4e oscillations due to alternating Josephson coupling and boson pairing, revealing conditions for these unique flux periodicities.

Contribution

It introduces a boson-based model for d-wave SQUIDs and demonstrates hc/4e oscillations arising from interface effects and boson pairing.

Findings

Observation of hc/4e oscillations in the model

Identification of parameter regions with boson binding

Correlation between boson pairing and flux oscillations

Abstract

We use a model of hard-core bosons to describe a SQUID built with two crystals of $d_{x^2-y^2}$-superconductors with orientations (100) and (110). Across the two faceted (100)/(110) interfaces, the structure of the superconducting order parameter leads to an alternating sign of the local Josephson coupling, and the possibility of quartet formation. Using a mapping of the boson model to an $XXZ$ model, we calculate numerically the energy of the system as a function of the applied magnetic flux, finding signals of $hc/4e$ oscillations in a certain region of parameters. This region has a large overlap to that at which binding of bosons exists.