Quantum Ice: A Quantum Monte Carlo Study

Shannon, Nic; Sikora, Olga; Pollmann, Frank; Penc, Karlo; Fulde, Peter

doi:10.1103/physrevlett.108.067204

Cited by 176 publications

(268 citation statements)

References 51 publications

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“…The effects of certain types of quantum fluctuations on the spin ice state have been investigated theoretically 12 and numerically 13,14 , where they have been demonstrated to lift the classical degeneracy and promote a three-dimensional (3D) QSL phase with low-energy gapless excitations that behave like photons 12,13 [15][16][17] . In an attempt to elucidate the microscopic underpinnings of these and related materials, recent theoretical studies have produced a general low-energy effective spin-1/2 model for magnetism in rare earth pyrochlores [18][19][20] .…”

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confidence: 99%

A two-dimensional spin liquid in quantum kagome ice

2015

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Actively sought since the turn of the century, two-dimensional quantum spin liquids (QSLs) are exotic phases of matter where magnetic moments remain disordered even at zero temperature. Despite ongoing searches, QSLs remain elusive, due to a lack of concrete knowledge of the microscopic mechanisms that inhibit magnetic order in materials. Here we study a model for a broad class of frustrated magnetic rare-earth pyrochlore materials called quantum spin ices. When subject to an external magnetic field along the [111] crystallographic direction, the resulting interactions contain a mix of geometric frustration and quantum fluctuations in decoupled two-dimensional kagome planes. Using quantum Monte Carlo simulations, we identify a set of interactions sufficient to promote a groundstate with no magnetic long-range order, and a gap to excitations, consistent with a Z 2 spin liquid phase. This suggests an experimental procedure to search for two-dimensional QSLs within a class of pyrochlore quantum spin ice materials.

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confidence: 99%

A two-dimensional spin liquid in quantum kagome ice

2015

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“…The classical nature of Ising spins precludes attainment of thermal equilibrium at temperatures (T) below the effective nearest neighbor energy scale J ff . Quantum fluctuations enhance dynamics and might allow coherent propagation of magnetic charge 12,13,14,15 , much as spinons in one-dimensional quantum magnets 16 .…”

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Quantum fluctuations in spin-ice-like Pr2Zr2O7

et al. 2013

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Spin ice is a magnetic analog of H 2 O ice that harbors dense static disorder. Dipolar interactions between classical spins yield a frozen frustrated state with residual configurational Pauling entropy and emergent magnetic monopolar quasiparticles. Introducing quantum fluctuations is of great interest as this could melt spin ice and allow coherent propagation of monopoles. Here, we report experimental evidence for quantum dynamics of magnetic monopolar quasiparticles in a new class of spin ice based on exchange interactions, Pr 2 Zr 2 O 7 . Narrow pinch point features in otherwise diffuse elastic neutron scattering reflects adherence to a divergence-free constraint for disordered spins on long time scales. Magnetic susceptibility and specific heat data correspondingly show exponentially activated behaviors. In sharp contrast to conventional ice, however, 490% of the neutron scattering is inelastic and devoid of pinch points furnishing evidence for magnetic monopolar quantum fluctuations.

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“…Quantum fluctuations are not expected to play a significant role for Ho 2 Ti 2 O 7 . However, for some pyrochlore materials strong quantum transverse fluctuations [8,9] could stabilize new magnetic states such as a quantum spin liquid for which new exotic excitations are expected [3,15,16,17,5].…”

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A novel type of splayed ferromagnetic order observed in Yb₂Ti₂O₇

Yaouanc

Réotier

Keller

et al. 2016

J. Phys.: Condens. Matter

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Abstract. The pyrochlore insulator Yb 2 Ti 2 O 7 has attracted the attention of experimentalists and theoreticians alike for about 15 years. Conflicting neutron diffraction data on the possible existence of magnetic Bragg reflections at low temperature have been published. Here we report the observation of magnetic Bragg reflections by neutron powder diffraction at 60 mK. The magnetic diffraction pattern is analyzed using representation theory. We find Yb 2 Ti 2 O 7 to be a splayed ferromagnet as reported for Yb 2 Sn 2 O 7 , a sibling compound with also dominating ferromagnetic interactions as inferred from the positive Curie-Weiss temperature. However, the configuration of the magnetic moment components perpendicular to the easy axis is of the all-in-all-out type in Yb 2 Ti 2 O 7 while it is two-in-two-out in Yb 2 Sn 2 O 7 . An overall experimental picture of the magnetic properties emerges. Introduction -The broad interest in geometrically frustrated magnetic materials such as pyrochlore insulator compounds R 2 M 2 O 7 (F d3m space group), where R is a rare earth ion and M a non magnetic element, arises from the large diversity of magnetic ground states and exotic fluctuations and excitations encountered [1,2,3,4,5]. This is due to the combined effects of the geometrical constraint resulting from the topology of the pyrochlore lattice and the action of the different possible interactions. As a consequence, classical and quantum fluctuations are particularly strong. Among the interactions of interest, the crystal field at the R position, the Heisenberg nearest-neighbour exchange interaction as well as its extension beyond the nearest-neighbour R ions [6,7], the anisotropy of the exchange interactions [8,9] and the inevitable dipolar interactions have been considered.The most remarkable discovery in the realm of geometrically frustrated magnetic materials has been the spin-ice ground state of Ho 2 Ti 2 O 7 in 1997 [10]. It is characterized by dipolar correlations emerging from the topological spin-ice constraint. This translates into pinch-points in the neutron diffuse scattering patterns [11] and magnetic monopole excitations [12,13,14].Because of its large ground-state degeneracy, a spin-ice compound does not order magnetically, i.e., it is in a so-called spin liquid state where the spins are strongly correlated although they do not display long range order. Quantum fluctuations are not expected to play a significant role for Ho 2 Ti 2 O 7 . However, for some pyrochlore materials strong quantum transverse fluctuations [8,9] could stabilize new magnetic states such as a quantum spin liquid for which new exotic excitations are expected [3,15,16,17,5].One of the favourite candidates for this exotic ground state is Yb 2 Ti 2 O 7 . Indeed, the exchange interactions are highly anisotropic, with a strong ferromagnetic component akin to the Ising exchange of spin ice [18].The dominating ferromagnetic component is also suggested by the positive Curie-Weiss temperature [19]. Remarkably, the Ising character of the exchan...

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Quantum Ice: A Quantum Monte Carlo Study

Cited by 176 publications

References 51 publications

A two-dimensional spin liquid in quantum kagome ice

A two-dimensional spin liquid in quantum kagome ice

Quantum fluctuations in spin-ice-like Pr2Zr2O7

A novel type of splayed ferromagnetic order observed in Yb₂Ti₂O₇

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Quantum Ice: A Quantum Monte Carlo Study

Cited by 176 publications

References 51 publications

A two-dimensional spin liquid in quantum kagome ice

A two-dimensional spin liquid in quantum kagome ice

Quantum fluctuations in spin-ice-like Pr2Zr2O7

A novel type of splayed ferromagnetic order observed in Yb2Ti2O7

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Product

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A novel type of splayed ferromagnetic order observed in Yb₂Ti₂O₇