Kagome lattice promotes chiral spin fluctuations

TL;DR

This study demonstrates that the kagomé lattice geometry significantly enhances chiral spin fluctuations, leading to observable Berry-phase effects in thermoelectric and electric transport, unlike in triangular lattices.

Contribution

It reveals how kagomé lattice geometry promotes net chiral spin fluctuations and Berry-phase phenomena at elevated temperatures, contrasting with previous models assuming continuous magnetization.

Findings

Enhanced chiral spin fluctuations in kagomé lattice materials.

Berry-phase effects are more pronounced due to lattice geometry.

Contrast with triangular lattice behavior in similar magnetic phases.

Abstract

Magnetic materials with tilted electron spins often exhibit conducting behavior that cannot be explained from semiclassical theories without invoking fictitious (emergent) electromagnetic fields. Quantum-mechanical models explaining such phenomena are rooted in the concept of a moving quasiparticle's Berry phase, driven by a chiral (left- or right-handed) spin-habit. Dynamical and nearly random spin fluctuations, with a slight bent towards left- or right-handed chirality, represent a promising route to realizing Berry-phase phenomena at elevated temperatures, but little is known about the effect of crystal lattice geometry on the resulting macroscopic observables. Here, we report thermoelectric and electric transport experiments on two metals with large magnetic moments on a triangular and on a slightly distorted kagom\'e lattice, respectively. We show that the impact of chiral spin fluctuations is strongly enhanced for the kagom\'e lattice. Both these spiral magnets have similar magnetic phase diagrams including a periodic array of magnetic skyrmions. However, our modelling shows that the geometry of the kagom\'e lattice, with corner-sharing spin-trimers, helps to avoid cancellation of Berry-phase contributions; spin fluctuations are endowed with a net chiral habit already in the thermally disordered (paramagnetic) state. Hence, our observations for the kagom\,e material contrast with theoretical models treating magnetization as a continuous field, and emphasize the role of lattice geometry on emergent electrodynamic phenomena.