Monopolar and dipolar relaxation in spin ice Ho2Ti2O7

Yishu Wang; T Reeder; Y Karaki; J Kindervater; T Halloran; N Maliszewskyj; Yiming Qiu; J A Rodriguez; S Gladchenko; S M Koohpayeh; S Nakatsuji; C Broholm

doi:10.1126/sciadv.abg0908

Monopolar and dipolar relaxation in spin ice Ho₂Ti₂O₇

Sci Adv. 2021 Jun 16;7(25):eabg0908. doi: 10.1126/sciadv.abg0908. Print 2021 Jun.

Authors

Yishu Wang^{1

2}, T Reeder³, Y Karaki⁴, J Kindervater³, T Halloran³, N Maliszewskyj², Yiming Qiu², J A Rodriguez^{2

5}, S Gladchenko², S M Koohpayeh^{3

6}, S Nakatsuji^{3

7

8

9}, C Broholm^{1

2

6}

Affiliations

¹ Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA. wangyishu@jhu.edu broholm@jhu.edu.
² NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
³ Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA.
⁴ Faculty of Education, University of the Ryukyus, Nishihara, Okinawa 903-0213, Japan.
⁵ Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742, USA.
⁶ Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, MD 21218, USA.
⁷ Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
⁸ Department of Physics, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
⁹ Trans-scale Quantum Science Institute, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.

Abstract

Ferromagnetically interacting Ising spins on the pyrochlore lattice of corner-sharing tetrahedra form a highly degenerate manifold of low-energy states. A spin flip relative to this "spin-ice" manifold can fractionalize into two oppositely charged magnetic monopoles with effective Coulomb interactions. To understand this process, we have probed the low-temperature magnetic response of spin ice to time-varying magnetic fields through stroboscopic neutron scattering and SQUID magnetometry on a new class of ultrapure Ho₂Ti₂O₇ crystals. Covering almost 10 decades of time scales with atomic-scale spatial resolution, the experiments resolve apparent discrepancies between prior measurements on more disordered crystals and reveal a thermal crossover between distinct relaxation processes. Magnetic relaxation at low temperatures is associated with monopole motion through the spin-ice vacuum, while at elevated temperatures, relaxation occurs through reorientation of increasingly spin-like monopolar bound states. Spin fractionalization is thus directly manifest in the relaxation dynamics of spin ice.

Copyright © 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).