Noncoplanar magnetic ordering driven by itinerant electrons on the pyrochlore lattice

TL;DR

This paper demonstrates that itinerant electrons on the pyrochlore lattice can stabilize complex noncoplanar magnetic orders with a quadrupled unit cell, driven by Fermi surface nesting at quarter filling.

Contribution

It reveals a novel mechanism where itinerant electrons induce noncoplanar magnetic order, contrasting with traditional fluctuation-driven magnetic structures in frustrated systems.

Findings

Noncoplanar magnetic order stabilized by electron Fermi surface nesting.

Order characterized by multiple wavevectors and definite handedness.

Potential existence of chiral spin liquid phase without magnetic order.

Abstract

Exchange interaction tends to favor collinear or coplanar magnetic orders in rotationally invariant spin systems. Indeed, such magnetic structures are usually selected by thermal or quantum fluctuations in highly frustrated magnets. Here we show that a complex noncoplanar magnetic order with a quadrupled unit cell is stabilized by itinerant electrons on the pyrochlore lattice. Specifically we consider the Kondo-lattice and Hubbard models at quarter filling. The electron Fermi 'surface' at this filling factor is topologically equivalent to three intersecting Fermi circles. Perfect nesting of the Fermi lines leads to magnetic ordering with multiple wavevectors and a definite handedness. The chiral order might persist without magnetic order in a chiral spin liquid at finite temperatures.