Indications of Unconventional Superconductivity in Doped and Undoped Triangular Antiferromagnets

TL;DR

This paper explores the potential for unconventional superconductivity in doped and undoped triangular antiferromagnets, highlighting the role of magnetic fluctuations and pairing symmetries through theoretical models.

Contribution

It demonstrates that exchange of paramagnons induces strong pairing correlations with specific symmetries in triangular lattice models, providing insights into possible superconducting states.

Findings

Strong d-wave singlet and s-wave triplet pairing correlations near half-filling.

Tendency for d-wave singlet pairing in interpolating t_1-t_2 models for certain ratios.

Implications for organic superconductors like κ-(BEDT-TTF)₂X.

Abstract

The possibility of superconductivity in doped and undoped triangular antiferromagnets is discussed. Using the Bethe-Salpeter (B-S) equation, it is shown that the exchange of RPA paramagnons on a triangular lattice Hubbard model leads to strong pairing correlations at and near half-filling. The dominant states for this system correspond to d-wave singlet (even-frequency) and s-wave triplet (odd-frequency) pairing. Analytical techniques applied to the hole-doped t-J model yield similar results. A t_1-t_2 Hubbard model interpolating between square (t_1=0) and triangular (t_1=t_2) lattices has a tendency to only d-wave singlet pairing for t_1/t_2 <= 0.8. Experimental consequences for organic compounds $\kappa$-(BEDT-TTF)$_2$X are discussed.