Effective Magnetic Monopoles and Universal Conductance Fluctuations

TL;DR

This paper demonstrates how to manipulate and detect effective magnetic monopoles in ferromagnets with strong spin-orbit coupling using universal conductance fluctuations, revealing a Berry phase signature.

Contribution

It introduces a method to control and observe effective magnetic monopoles via UCF measurements in ferromagnets, providing new insights into their physical consequences.

Findings

Reproducible quasiperiodic oscillations as a function of magnetization direction.

Identification of a Berry phase fingerprint of magnetic monopoles.

Manipulation of monopoles with external magnetic fields.

Abstract

The observation of isolated positive and negative charges, but not isolated magnetic north and south poles, is an old puzzle. Instead, evidence of effective magnetic monopoles has been found in the abstract momentum space. Apart from Hall-related effects, few observable consequences of these abstract monopoles are known. Here, we show that it is possible to manipulate the monopoles by external magnetic fields and probe them by universal conductance fluctuation (UCF) measurements in ferromagnets with strong spin-orbit coupling. The observed fluctuations are not noise, but reproducible quasiperiodic oscillations as a function of magnetisation direction, a novel Berry phase fingerprint of the magnetic monopoles.