$z = 3$ antiferromagnetic quantum criticality and emergence of fermionized skyrmions

Abstract

Hertz-Moriya-Millis theory with dynamical critical exponent $z = 2$ has been proposed to describe antiferromagnetic quantum criticality in itinerant electron systems. In this study we show that the dynamical critical exponent changes from $z = 2$ to $z = 3$ at low temperatures, which results from effective long-range interactions between spin fluctuations, generated by Fermi-surface fluctuations beyond the Eliashberg framework. We claim that the underlying physics for the $z = 3$ antiferromagnetic quantum criticality is the emergence of fermionized skyrmion excitations at low energies, which form a Fermi surface, referred as a skyrmion liquid, where the interplay between itinerant electrons and skyrmions is argued to allow fermionized skyrmions. We construct a dual field theory in terms of skyrmion excitations, and obtain the $z = 3$ antiferromagnetic quantum criticality. This demonstration suggests the expected but nontrivial consistency between weak-coupling and strong-coupling theories.