Effective Magnetic Monopoles and Universal Conductance Fluctuations

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.

Final version accepted by Physical Review Letters

References in corpus (9)

• Anomalous Hall effect
• Theory of ferromagnetic (III,Mn)V semiconductors
• Wave-packet dynamics in slowly perturbed crystals: Gradient corrections and Berry-phase effects
• Anomalous Hall Effect and Magnetic Monopoles in Momentum-Space
• Weak localization in ferromagnetic (Ga,Mn)As nanostructures
• Universal conductance fluctuations in epitaxial GaMnAs ferromagnets: structural and spin disorder
• Conductance fluctuations in diffusive rings: Berry phase effects and criteria for adiabaticity
• The effect of the spin-orbit geometric phase on the spectrum of Aharonov-Bohm oscillations in a semiconductor mesoscopic ring
• External Control of a Metal-Insulator Transition in GaMnAs Wires

Cited by in corpus (6)

• Ab Initio Theory of Scattering-Independent Anomalous Hall Effect
• Effective Quantum Theories for Transport in Inhomogeneous Systems with Non-trivial Band Structure
• Magnetic monopole bibliography
• Mechanism of Universal Conductance Fluctuations
• Direct probing of band-structure Berry phase in diluted magnetic semiconductors
• Spectral analysis of universal conductance fluctuations