Bipolaron Density-Wave Driven By Antiferromagnetic Correlations and Frustration in Organic Superconductors

TL;DR

This paper discusses the Paired Electron Crystal (PEC), a charge-ordered bipolaron density wave in frustrated 2D systems, and how increased frustration induces a transition from PEC to superconductivity in organic materials.

Contribution

It introduces the concept of PEC as a bipolaron density wave driven by magnetic correlations and frustration, linking it to superconductivity in organic charge-transfer solids.

Findings

PEC observed in insulating states near superconductivity

Frustration drives PEC-to-superconductor transition

PEC characterized as a bipolaron density wave

Abstract

We describe the Paired Electron Crystal (PEC) which occurs in the interacting frustrated two-dimensional 1/4-filled band. The PEC is a charge-ordered state with nearest-neighbor spin singlets separated by pairs of vacant sites, and can be thought of as a bipolaron density wave. The PEC has been experimentally observed in the insulating state proximate to superconductivity in the organic charge-transfer solids. Increased frustration drives a PEC-to-superconductor transition in these systems.