Functional renormalization group for the anisotropic triangular antiferromagnet

TL;DR

This paper introduces a functional renormalization group method to analyze frustrated magnetic systems on large lattices, revealing phase transitions in the anisotropic triangular antiferromagnet model.

Contribution

The study develops a scalable RG scheme for large lattice frustrated magnets and maps out the phase diagram of the anisotropic triangular lattice model.

Findings

Identified a second-order transition from Neel to spiral order at xi=0.6-0.7.

Detected a first-order transition to a disordered phase at xi=1.1.

Mapped the phase diagram of the anisotropic triangular antiferromagnet.

Abstract

We present a functional renormalization group scheme that allows us to calculate frustrated magnetic systems of arbitrary lattice geometry beyond O(200) sites from first principles. We study the magnetic susceptibility of the antiferromagnetic (AFM) spin-1/2 Heisenberg model ground state on the spatially anisotropic triangular lattice, where J' denotes the coupling strength of the intrachain bonds along one lattice direction and J the coupling strength of the interchain bonds. We identify three distinct phases of the Heisenberg model. Increasing xi=J'/J from the effective square lattice xi=0, we find an AFM Neel order to spiral order transition at xi_{c1} = 0.6-0.7, with indication to be of second order. In addition, above the isotropic point at xi_{c2} = 1.1, we find a first order transition to a magnetically disordered phase with collinear AFM stripe fluctuations.