Repulsion-Sustained Supercurrent and Flux Quantization in Rings of Symmetric Hubbard Clusters

TL;DR

This paper investigates flux quantization and supercurrent phenomena in symmetric Hubbard cluster rings, revealing conditions under which superconducting flux quantization occurs and confirming theoretical predictions with numerical methods.

Contribution

It introduces a novel exact-diagonalization technique for many-fermion problems and demonstrates superconducting flux quantization in Hubbard cluster rings.

Findings

Superconducting flux quantization observed with O-O hopping.

Bound pair propagation hindered with Cu-Cu links due to symmetry.

Results support W=0 pairing theory.

Abstract

We test the response to a threading magnetic field of rings of 5-site $C_{4v}$-symmetric repulsive Hubbard clusters connected by weak intercell links; each 5-site unit has the topology of a CuO$_{4}$ cluster and a repulsive interaction is included on every site. In a numerical study of the three-unit ring with 8 particles, we take advantage of a novel exact-diagonalization technique which can be generally applied to many-fermion problems. For O-O hopping we find Superconducting Flux Quantization (SFQ), but for purely Cu-Cu links bound pair propagation is hindered by symmetry. The results agree with W=0 pairing theory.