Quantum critical behavior of clean itinerant ferromagnets

TL;DR

This paper investigates the quantum critical behavior of clean itinerant ferromagnets, revealing breakdown of traditional theories due to electron interactions and deriving exact scaling laws for the quantum critical point.

Contribution

It introduces a new understanding of quantum criticality in clean itinerant ferromagnets by accounting for singular electron interactions and long-range correlations.

Findings

Effective long-range interactions of form 1/r^{2d-1} are generated.

Unusual scaling behavior at the quantum critical point in 1<d≤3 is derived.

Multiple temperature scales characterize the quantum-to-classical crossover.

Abstract

We consider the quantum ferromagnetic transition at zero temperature in clean itinerant electron systems. We find that the Landau-Ginzburg-Wilson order parameter field theory breaks down since the electron-electron interaction leads to singular coupling constants in the Landau-Ginzburg-Wilson functional. These couplings generate an effective long-range interaction between the spin or order parameter fluctuations of the form 1/r^{2d-1}, with d the spatial dimension. This leads to unusual scaling behavior at the quantum critical point in 1 < d\leq 3, which we determine exactly. We also discuss the quantum-to-classical crossover at small but finite temperatures, which is characterized by the appearance of multiple temperature scales. A comparison with recent results on disordered itinerant ferromagnets is given.