"Anomalous Fermi-liquid phase in metallic skyrmion crystals"

Haruki Watanabe: S. A. Parameswaran, S. Raghu, and Ashvin Vishwanath; Physical Review B, 07/30/14.

Additional Authors: S. A. Parameswaran, S. Raghu, and Ashvin Vishwanath

Abstract:

In noncentrosymmetric crystals such as MnSi, magnetic order can take the form of a skyrmion crystal (SkX). In this phase, conduction electrons coupled to the local magnetic moments acquire a Berry phase, leading to an emergent electromagnetism. Motivated by experimental reports of a non-Fermi-liquid phase in MnSi, in which resistivity is observed to scale as ΔρT3/2, here we examine the effect of coupling phonons of an incommensurate SkX to electrons. Despite the formal similarity to a system consisting of a Fermi surface coupled to an electromagnetic field, the Berry phase fluctuations do not lead to non-Fermi-liquid behavior. Instead, we propose a different mechanism in which electrons scatter off columnar fluctuation in a three-dimensional SkX. When the effects of lattice-induced anisotropy are neglected, these fluctuations are ultrasoft and induce an “anomalous Fermi liquid” in which Landau quasiparticles survive but with an anomalous Δρ(T)∼T7/4 resistivity perpendicular to the columns, and a Fermi-liquid resistivity along them.