Frustrated Spin System in theta-(BEDT-TTF)_2RbZn(SCN)_4

TL;DR

This paper investigates the origin of the spin gap in theta-(BEDT-TTF)_2RbZn(SCN)_4, showing that magnetic frustration among localized spins may lead to the observed spin gap behavior.

Contribution

It provides a theoretical analysis using Hartree-Fock approximation to reveal spin frustration as a key factor in the spin gap formation.

Findings

Antiferromagnetic order stabilized between certain dimers.

Effective localized spin 1/2 model constructed.

Frustration among spins may cause the spin gap.

Abstract

The origin of the spin gap behavior in the low-temperature dimerized phase of theta-(BEDT-TTF)_2RbZn(SCN)_4 has been theoretically studied based on the Hartree-Fock approximation for the on-site Coulomb interaction at absolute zero. Calculations show that, in the parameter region considered to be relevant to this compound, antiferromagnetic ordering is stabilized between dimers consisting of pairs of molecules coupled with the largest transfer integral. Based on this result an effective localized spin 1/2 model is constructed which indicates the existence of the frustration among spins. This frustration may result in the formation of spin gap.