Observation of Magnetic Monopoles in Spin Ice

Kadowaki, Hiroko; Doi, Naohiro; Aoki, Yuji; Tabata, Yoshikazu; Sato, Taku; Lynn, J. W.; Matsuhira, Kazuyuki; Hiroi, Zenji

doi:10.1143/jpsj.78.103706

Cited by 176 publications

(159 citation statements)

References 21 publications

(63 reference statements)

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“…For this reason, spin ice offers a beautiful realisation of classical magnetostatics, with local violations of the ice rules entering as point magnetic charges (magnetic monopoles [11][12][13][14][15][16][17] ) and spin correlations which exhibit "pinch point" singularities in k-space…”

Section: Introductionmentioning

confidence: 99%

Seeing the light: Experimental signatures of emergent electromagnetism in a quantum spin ice

2012

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The "spin ice" state found in the rare earth pyrochlore magnets Ho2Ti2O7 and Dy2Ti2O7 offers a beautiful realisation of classical magnetostatics, complete with magnetic monopole excitations. It has been suggested that in "quantum spin ice" materials, quantum-mechanical tunnelling between different ice configurations could convert the magnetostatics of spin ice into a quantum spin liquid which realises a fully dynamical, latticeanalogue of quantum electromagnetism. Here we explore how such a state might manifest itself in experiment, within the minimal microscopic model of a such a quantum spin ice. We develop a lattice field theory for this model, and use this to make explicit predictions for the dynamical structure factor which would be observed in neutron scattering experiments on a quantum spin ice. We find that "pinch points", which are the signal feature of a classical spin ice, fade away as a quantum ice is cooled to its zero-temperature ground state. We also make explicit predictions for the ghostly, linearly dispersing magnetic excitations which are the "photons" of this emergent electromagnetism. The predictions of this field theory are shown to be in quantitative agreement with Quantum Monte Carlo simulations at zero temperature.

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Section: Introductionmentioning

confidence: 99%

Seeing the light: Experimental signatures of emergent electromagnetism in a quantum spin ice

2012

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“…By tiling these tiny magnets in specific geometrical arrangements, it is possible to create physical properties and functionalities not displayed by the constituent materials [1]. For instance, it has been recently demonstrated that artificial spin ice structures can display glass-like behaviour [3,4], configurable charge ordering [5] and topological structures that can be analogous to magnetic monopoles [6,7] and Dirac strings [8,9].…”

Section: Introductionmentioning

confidence: 99%

Apparent ferromagnetism in the pinwheel artificial spin ice

et al. 2018

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Magnetic artificial spin ice provides examples of how competing interactions between magnetic nanoelements can lead to a range of fascinating and unusual phenomena. We examine theoretically a class of spin ice tilings, called pinwheel, for which near degeneracy of spin configuration energies can be achieved. The pinwheel tiling is a simple but crucial variant on the square ice geometry, in which each nanoelement of square ice is rotated some angle about its midpoint. Surprisingly, this rotation leads to an intriguing phase transition; and even though the spins are not parallel to one another, a ferromagnetic phase is found for rotation angles near 45• . Here, magnetic domains and domain walls are found when viewed in terms of net magnetisation. Moreover, the ferromagnetic behaviour of the system depends on its anisotropy which we can control by array shape and size.

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“…Its emerging gapless fractionalized excitations are called spinons 13 . The concept of fractional excitations has been applied to magnetic monopoles in spin ice [14][15][16][17] , kagome and hyper-kagome lattices 18 , the quantum Hall effect [19][20][21][22] , conducting polymers 23,24 , and even to certain spin arrays with local spin larger than 1/2 (refs 25, 26). For the prototypical spin-1/2 Heisenberg antiferromagnetic chain, exact calculations of the dynamic structure factor over the whole range of the spectrum have become available.…”

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confidence: 99%

Fractional spinon excitations in the quantum Heisenberg antiferromagnetic chain

et al. 2013

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One of the simplest quantum many-body systems is the spin-1/2 Heisenberg antiferromagnetic chain, a linear array of interacting magnetic moments. Its exact ground state is a macroscopic singlet entangling all spins in the chain. Its elementary excitations, called spinons, are fractional spin-1/2 quasiparticles created and detected in pairs by neutron scattering. Theoretical predictions show that two-spinon states exhaust only 71% of the spectral weight and higher-order spinon states, yet to be experimentally located, are predicted to participate in the remaining. Here, by accurate absolute normalization of our inelastic neutron scattering data on a spin-1/2 Heisenberg antiferromagnetic chain compound, we account for the full spectral weight to within 99(8)%. Our data thus establish and quantify the existence of higher-order spinon states. The observation that, within error bars, the experimental line shape resembles a rescaled two-spinon one with similar boundaries allows us to develop a simple picture for understanding multi-spinon excitations.O ne hundred years ago, Max von Laue and co-workers discovered X-ray diffraction 1 , thereby giving birth to the field of crystallography to which we owe much of our understanding of materials on the atomic scale. The very first diffraction image was recorded from a single crystal of copper sulphate pentahydrate 1,2 . In addition to vast practical use including herbicide, wood impregnation and algae control in swimming pools, copper sulphate also carries great educational importance. Generations of school children have been inspired in chemistry classes across the globe by growing from evaporating solution beautiful blue crystals of copper sulphate (in 2008, artist Roger Hiorns created an installation called Seizure 3 covering an entire apartment in copper sulphate crystals). When cooled close to absolute zero temperature, copper sulphate has even more fascinating lessons to teach-it becomes a quantum spin liquid. Moreover, it materializes one of the simplest models hosting complex quantum many-body physics, the one-dimensional spin-1/2 Heisenberg antiferromagnet, for which there exists an exact analytic solution-namely the Bethe ansatz 4 . Quantum spin liquid ground states entangle a macroscopic number of spins and give rise to astonishing and counterintuitive phenomena. Quantum spin liquids occur in a variety of contexts ranging from the quantum spin Hall effect 5,6 and high-T c superconductivity 7-9 to confined ultracold gases and carbon nanotubes 10 . A particularly clear form of a gapless algebraic quantum spin liquid is realized in a one-dimensional array of spins-1/2 that are coupled by nearest-neighbour isotropic exchange, the spin-1/2 Heisenberg antiferromagnetic chain. At zero temperature, this spin liquid is critical with respect to long-range antiferromagnetic order as well as with respect to dimerization 11,12 . Its emerging gapless fractionalized excitations are called spinons 13 . The concept of fractional excitations has been applied to magnetic monopoles ...

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Observation of Magnetic Monopoles in Spin Ice

Cited by 176 publications

References 21 publications

Seeing the light: Experimental signatures of emergent electromagnetism in a quantum spin ice

Seeing the light: Experimental signatures of emergent electromagnetism in a quantum spin ice

Apparent ferromagnetism in the pinwheel artificial spin ice

Fractional spinon excitations in the quantum Heisenberg antiferromagnetic chain

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