Incommensurate spiral magnetic order on anisotropic triangular lattice: Dynamical mean field study in a spin-rotating frame

TL;DR

This study investigates the incommensurate spiral magnetic order in the half-filled Hubbard model on an anisotropic triangular lattice using dynamical mean-field theory and DMRG, revealing the persistence of spiral order across a range of parameters and highlighting the effects of electron fluctuations.

Contribution

It provides a detailed DMFT analysis of incommensurate magnetic order on an anisotropic triangular lattice, incorporating dynamical fluctuations with DMRG as an impurity solver, which was not previously explored.

Findings

Incommensurate spiral order persists for $t'/t \,\gtrsim\, 0.7$ across the insulator-metal transition.

Magnetic moment reduction is significant near the N\'eel to spiral phase boundary.

Magnetic moment peaks then decreases with increasing $t'/t$, including at the isotropic point $t'/t=1$.

Abstract

We study the ground-state magnetism of the half-filled Hubbard model on the anisotropic triangular lattice, where two out of three bonds have hopping $t$ and the third one has $t^\prime$ in a unit triangle. Working in a spin-rotating frame and using the density matrix renormalization group method as an impurity solver, we provide a proper description of incommensurate magnetizations at zero temperature in the framework of the dynamical mean-field theory (DMFT). It is shown that the incommensurate spiral magnetic order for $t^\prime/t\gtrsim 0.7$ survives the dynamical fluctuations of itinerant electrons in the Hubbard interaction range from the strong-coupling (localized-spin) limit down to the insulator-to-metal transition. We also find that the magnetic moment reduction from the localized-spin limit is pronounced in the vicinity of the transition between the commensurate N\'eel and incommensurate spiral phases at $t^\prime/t\sim 0.7$. When the anisotropy parameter $t^\prime/t$ increases from the N\'eel-to-spiral transition, the magnitude of the magnetic moment immediately reaches a maximum and then rapidly decreases in the range of larger $t^\prime/t$ including the isotropic triangular lattice point $t^\prime/t=1$. This work gives a solid foundation for further extension of the study including nonlocal correlation effects neglected at the standard DMFT level.