Test for Pairing Symmetry Based on Spin Fluctuations in Organic Superconductors $\kappa$-(BEDT-TTF)$_{2}$X

TL;DR

This paper proposes a method to determine the pairing symmetry in organic superconductors by analyzing the momentum space position of spin susceptibility peaks, linking them to the superconducting state symmetry and Fermi surface geometry.

Contribution

It introduces a novel approach to identify pairing symmetry using spin susceptibility measurements and demonstrates distinct spin response patterns for different pairing states.

Findings

Different incommensurate spin response patterns for d_{x^{2}-y^{2}} and d_{xy} pairing.

Prediction of no spin resonance mode in the studied organic superconductor.

Method links spin susceptibility peaks to pairing symmetry and Fermi surface geometry.

Abstract

We propose that the superconducting pairing symmetry of organic superconductors $\kappa$-(BEDT-TTF)$_{2}$X can be determined by measuring the position in momentum space of the incommensurate peaks of the spin susceptibility. We show that the positions of these peaks are uniquely determined by the symmetry of the superconducting state and the geometry of Fermi surface. Based on the effective Hubbard model on an anisotropic triangular lattice, we demonstrate the different incommensurate patters of spin responses for $d_{x^{2}-y^{2}}$- and $d_{xy}$-like pairing states. In addition, we predict the nonexistence of the spin resonance mode in this compound, which is an important feature in high-$T_{c}$ superconductors.