Spin-liquid and magnetic phases in the anisotropic triangular lattice: the case of $\kappa$-(ET)$_2$X

TL;DR

This study investigates the ground-state magnetic properties of the anisotropic triangular lattice Hubbard model relevant to organic salts, revealing non-magnetic and magnetic phases depending on frustration levels using advanced Monte Carlo methods.

Contribution

It applies a novel Monte Carlo approach with backflow correlations to analyze magnetic phases in the anisotropic triangular lattice Hubbard model, providing new insights into frustration effects.

Findings

No magnetic order at high interaction and frustration ratio (t'/t=0.85).

Néel order appears at lower frustration ratios (t'/t=0.4-0.6).

Results match experimental observations in specific organic salts.

Abstract

The two-dimensional Hubbard model on the anisotropic triangular lattice, with two different hopping amplitudes $t$ and $t^\prime$, is relevant to describe the low-energy physics of $\kappa$-(ET)$_2$X, a family of organic salts. The ground-state properties of this model are studied by using Monte Carlo techniques, on the basis of a recent definition of backflow correlations for strongly-correlated lattice systems. The results show that there is no magnetic order for reasonably large values of the electron-electron interaction $U$ and frustrating ratio $t^\prime/t = 0.85$, suitable to describe the non-magnetic compound with X=Cu$_2$(CN)$_3$. On the contrary, N\'eel order takes place for weaker frustrations, i.e., $t^\prime/t \sim 0.4 \div 0.6$, suitable for materials with X=Cu$_2$(SCN)$_2$, Cu[N(CN)$_2$]Cl, or Cu[N(CN)$_2$]Br.