2019/11/30 by Matthew Stern, Claudio Castelnovo, Roderich Moessner +2
Physics and Astronomy · #Advanced Condensed Matter Physics #Magnetic monopole #Physics #Physics of Superconductivity and Magnetism #Quantum #Quantum many-body systems #Quantum mechanics #Spin (aerodynamics) #Spin ice #cond-mat.dis-nn #cond-mat.stat-mech #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.104.115114
published as Phys. Rev. B 104, 115114 (2021) · 12 pages, 11 figures
openalex created_date 2019/11/22 · openalex publication_date 2021/09/07 · arxiv created 2021/09/10 · arxiv updated 2021/09/13 · openalex updated_date 2026/08/06
We consider quantum spin ice in a temperature regime in which its response is dominated by the coherent motion of a dilute gas of monopoles through an incoherent spin background, taken to be quasistatic on the relevant timescales. The latter introduces well-known blocked directions that we find sufficient to reduce the coherent propagation of monopoles to quantum diffusion. This result is robust against disorder, as a direct consequence of the ground-state degeneracy, which disrupts the quantum interference processes needed for weak localization. Moreover, recent work [Tomasello et al., Phys. Rev. Lett. 123, 067204 (2019)] has shown that the monopole hopping amplitudes are roughly bimodal: for \ensuremath≈1/3 of the flippable spins surrounding a monopole, these amplitudes are extremely small. We exploit this structure to construct a theory of quantum monopole motion in spin ice. In the limit where the slow hopping terms are set to zero, the monopole wave functions appear to be fractal; we explain this observation via mapping to quantum percolation on trees. The fractal, nonergodic nature of monopole wave functions manifests itself in the low-frequency behavior of monopole spectral functions, and is consistent with experimental observations.