Hidden multiple-spin interactions as an origin of spin scalar chiral order in frustrated Kondo lattice models

Phys Rev Lett. 2012 Mar 2;108(9):096401. doi: 10.1103/PhysRevLett.108.096401. Epub 2012 Feb 27.

Abstract

We reveal the significance of kinetic-driven multiple-spin interactions hidden in geometrically frustrated Kondo lattice models. Carefully examining the perturbation in terms of the spin-charge coupling up to the fourth order, we find that a positive biquadratic interaction is critically enhanced and plays a crucial role on stabilizing a spin scalar chiral order near 1/4 filling in a triangular lattice case. This is a generalized Kohn anomaly, appearing only when the second-order perturbation is inefficient because of the degeneracy under frustration. The mechanism is potentially common to frustrated spin-charge coupled systems, leading to emergence of unusual magnetic orders.