Superconductivuty versus Tunneling in a Doped Antiferromagnetic Ladder

TL;DR

This paper models charge excitations in a doped antiferromagnetic ladder using interacting spinless fermions, revealing how hole pairing relates to charge gaps and tunneling suppression, with implications for superconductivity.

Contribution

It introduces a model of charge excitations with spinless fermions on a ladder, linking hole pairing to charge gaps and tunneling behavior, and explores conditions for superconducting or crystalline states.

Findings

Hole pairing coincides with a single-particle charge gap.

Absence of coherent inter-chain tunneling when pairs form.

Hole pairs can condense into superconducting or crystalline states.

Abstract

The low-energy charge excitations of a doped antiferromagnetic ladder are modeled by a system of interacting spinless fermions that live on the same ladder. A relatively large spin gap is assumed to ``freeze out'' all spin fluctuations. We find that the formation of rung hole pairs coincides with the opening of a single-particle gap for charge excitations along chains and with the absence of coherent tunneling in between chains. We also find that such hole pairs condense into either a crystalline or superconducting state as a function of the binding energy.