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

Area of Science:

• Condensed matter physics
• Materials science

Background:

• Electrons on honeycomb or triangular lattices are crucial for understanding novel electronic phases.
• Spin density wave (SDW) order is a key phenomenon in correlated electron systems.

Purpose of the Study:

• Investigate the nature of the spin density wave (SDW) phase in electrons doped to the saddle point of a band structure.
• Characterize the symmetry breaking and electronic properties of the emergent SDW phase.

Main Methods:

• Theoretical analysis of electrons on honeycomb and triangular lattices.
• Investigation of system parameters leading to SDW order below a critical temperature T(N).

Main Results:

• A uniaxial SDW phase emerges at temperatures T≤T(N), breaking O(3)×Z(4) symmetry.
• The SDW phase exhibits an eight-site unit cell with nonuniform spin moments.
• The system becomes a half-metal, preserving the Fermi surface but with spin-polarized gapless excitations.

Conclusions:

• The discovered uniaxial SDW phase offers a novel state for condensed matter physics.
• This half-metallic phase allows for electrical control of spin currents, with potential applications in nanoscience.