Fragmented Cooper pair condensation in striped superconductors

TL;DR

This paper demonstrates that in striped superconductors modeled by the two-dimensional t-t'-J model, the superconducting condensate is naturally fragmented into partial condensates on stripes, revealing a complex interplay between stripe order and superconductivity.

Contribution

It introduces the concept of natural fragmentation of the superconducting condensate in striped systems and uses DMRG to analyze the ground state in a specific strongly correlated electron model.

Findings

Condensate is fragmented into partial condensates on stripes.

Fragments hybridize to form an extended macroscopic wave function.

Results connect stripe order with superconductivity in strongly correlated systems.

Abstract

Condensation of bosons in Bose-Einstein condensates or Cooper pairs in superconductors refers to a macroscopic occupation of a few single- or two-particle states. A condensate is called "fragmented" if not a single, but multiple states are macroscopically occupied. While fragmentation is known to occur in particular Bose-Einstein condensates, we propose that fragmentation naturally takes place in striped superconductors. To this end, we investigate the nature of the superconducting ground state realized in the two-dimensional $t$-$t^\prime$-$J$ model. In the presence of charge density modulations, the condensate is shown to be fragmented and composed of partial condensates located on the stripes. The fragments of the condensates hybridize to form an extended macroscopic wave function across the system. The results are obtained from evaluating the singlet-pairing two-particle density matrix of the ground state on finite cylinders computed via the density matrix renormalization group (DMRG) method. Our results shed light on the intricate relation between stripe order and superconductivity in systems of strongly correlated electrons.