Itinerant half-metal spin-density-wave state on the hexagonal lattice

TL;DR

This paper explores a novel itinerant half-metal spin-density-wave state on honeycomb and triangular lattices, revealing a uniaxial SDW phase with unique symmetry breaking and potential for electrical spin control.

Contribution

It introduces a new SDW state with uniaxial order on hexagonal lattices, characterized by an eight-site unit cell and half-metallic properties, expanding understanding of magnetic phases in doped systems.

Findings

The SDW state breaks $O(3) imes Z_4$ symmetry.

It features an eight-site unit cell with non-uniform spin moments.

The state is a half-metal with gapless excitations in one spin branch.

Abstract

We consider electrons on a honeycomb or triangular lattice doped to the saddle point of the bandstructure. We assume system parameters are such that spin density wave (SDW) order emerges below a temperature $T_N$ and investigate the nature of the SDW phase. We argue that at $T < T_N$ the system develops a uniaxial SDW phase whose ordering pattern breaks $O(3) \times Z_4$ symmetry and corresponds to an eight site unit cell with non-uniform spin moments on different sites. This state is a half-metal -- it preserves full original Fermi surface, but has gapless charged excitations in one spin branch only. It allows for electrical control of spin currents and is desirable for nano-science.