On the Spin Gap Phase in lambda-(BETS)_2GaX_zY_{4-z}

TL;DR

This paper investigates the insulating spin gap phase in a quasi-two-dimensional organic conductor, combining theoretical calculations and simulations to understand its magnetic properties and phase boundaries.

Contribution

It provides a theoretical analysis of the spin gap phase using Hartree-Fock and quantum Monte Carlo methods, clarifying the system's position near phase boundaries.

Findings

System is near the boundary between antiferromagnetic and spin gap phases.

Insulating state arises from strong Coulomb interactions and spin ordering.

Experimental observations can be explained by the proximity to phase transition.

Abstract

The nature of the insulating ground state in quasi-two-dimensional organic conductor lambda-(BETS)_2GaX_zY_{4-z}, where the existence of a spin gap is suggested by susceptibility measurement, has been studied theoretically. Hartree-Fock calculations at absolute zero temperature show that if the on-site Coulomb interaction exceeds some critical value, then antiferromagnetic spin ordering emerges and eventually leads to an insulating state which can be considered as a two-dimensional localized spin system. Based on the quantum Monte Carlo simulations of Katoh and Imada, we will show that this system locates near the boundary between the antiferromagnetic phase and the spin gap phase, so that experimental facts can be explained.