title: Hidden multiple-spin interactions as an origin of spin scalar chiral order in frustrated Kondo lattice models.
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.
authors.affiliation: Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan. akagi@aion.t.u-tokyo.ac.jp
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Akagi
authors.forename: Masafumi
authors.initials: M
authors.lastname: Udagawa
authors.forename: Yukitoshi
authors.initials: Y
authors.lastname: Motome