Magnetic monopole dynamics in spin ice: An experimental study
| When |
Jan 27, 2020
from 11:00 to 12:00 |
|---|---|
| Where | Amphi. Schrödinger |
| Attendees |
Elsa Lhotel |
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Among the original magnetic states which emerge from frustrated magnetic systems, spin ice has aroused a strong interest because beyond its macroscopically degenerate ground state, the excitations can be described as magnetic charges, called magnetic monopoles. At very low temperature, below 200 mK, spin ice dynamics is governed by these monopoles. By performing thermal quenches in spin ice compounds down to these temperatures, through a specific protocol called “avalanche quench” [1], we are able to prepare samples with a very large out-of-equilibrium density of metastable magnetic monopoles. We used this method to study the monopole dynamics in the spin ice compounds Dy2Ti2O7 and Ho2Ti2O7, and could measure the monopole current as a function of magnetic field by magnetization measurements [2]. In this talk, I will first introduce the rich physics of spin ice and its excitations. Then, I will present some of our recent results which show that even below 200 mK, there is a fast recombination of magnetic monopoles. The comparison between magnetic relaxation measurements performed on several samples with different isotopes gives insights on the quantum tunneling mechanism governing the hopping of monopoles on the lattice, and shows the role of the dynamic coupling between the hyperfine fields and the electronic spins associated with magnetic monopoles [3].
[1] C. Paulsen et al., Nature Physics 10, 135 (2014)
[2] C. Paulsen et al., Nature Physics 12, 661 (2016)
[3] C. Paulsen et al., Nature Communications 10, 1509 (2019)