Fragmentation in Frustrated Magnets: A Review

Lhotel, Elsa; Jaubert, Ludovic D. C.; Holdsworth, Peter

doi:10.1007/s10909-020-02521-3

Cited by 29 publications

(24 citation statements)

References 133 publications

(300 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…( 5), a finite θ parameter requires Q = 0. Classically, such order can coexist with Coulomb liquid behavior, for example, in the fragmented phase of spin ice [60,61], which has been recently observed in iridate materials [62][63][64]. Our long-wavelength symmetry analysis suggests that the quantum limit of a fragmented spin liquid on breathing pyrochlore would be a U (1) QSL phase with both a θ-term and a dynamical axion.…”

supporting

confidence: 56%

Dynamical Axions in $U(1)$ Quantum Spin Liquids

Pace¹,

Castelnovo²,

Laumann³

2021

Preprint

View full text Add to dashboard Cite

Since their proposal nearly half a century ago, physicists have sought axions in both high energy and condensed matter settings. Despite intense and growing efforts, to date experimental success has been limited, with the most prominent results arising in the context of topological insulators.Here we propose a novel mechanism whereby axions can be realized in quantum spin liquids. We discuss the necessary symmetry requirements and identify possible experimental realizations in candidate pyrochlore materials, such as Ba 3 Yb 2 Zn 5 O 11 . In this context, the axions couple both to the external and to the emergent electromagnetic fields. We show that the interaction between the axion and the emergent photon leads to a characteristic dynamical response, which can be measured experimentally in inelastic neutron scattering. This work sets the stage for studying axion electrodynamics in the highly tunable setting of frustrated magnets.

show abstract

supporting

confidence: 56%

Dynamical Axions in $U(1)$ Quantum Spin Liquids

Pace¹,

Castelnovo²,

Laumann³

2021

Preprint

View full text Add to dashboard Cite

show abstract

“…From the "two-in-two-out" picture, flipping a single spin leads to the creation of two magnetic monopoles at the centers of each of the resulting "3-in-1-out" and "1-in-3-out" tetrahedra. When the monopole density is high, the energy is minimized via the creation of a fragmented state where a crystal of monopoles coexists with a Coulomb spin liquid [16]. Alternatively, this phase can be understood through the superposition of two components: an ordered, divergence-full "all-in-all-out" (AIAO) component and a divergence-free "two-in-two-out" component, which remains fluctuating and provides a gain in entropy [17].…”

Section: Introductionmentioning

confidence: 99%

Absence of moment fragmentation in the mixed B -site pyrochlore Nd2GaSbO7

et al. 2021

View full text Add to dashboard Cite

Nd-based pyrochlore oxides of the form Nd 2 B 2 O 7 have garnered a significant amount of interest owing to the moment fragmentation physics observed in Nd 2 Zr 2 O 7 and speculated in Nd 2 Hf 2 O 7 . Notably this phenomenon is not ubiquitous in this family, as it is absent in Nd 2 Sn 2 O 7 , which features a smaller ionic radius on the B site. Here, we explore the necessary conditions for moment fragmentation in the Nd pyrochlore family through a detailed study of the mixed B-site pyrochlore Nd 2 GaSbO 7 . The B site of this system is characterized by significant disorder and an extremely small average ionic radius. Similarly to Nd 2 Sn 2 O 7 , we find no evidence for moment fragmentation through our bulk characterization and neutron scattering experiments, indicating that chemical pressure (and not necessarily the B-site disorder) plays a key role in the presence or absence of this phenomenon in this material family. Surprisingly, the presence of significant B-site disorder in Nd 2 GaSbO 7 does not generate a spin-glass ground state and instead the same all-in-all-out magnetic order identified in other Nd pyrochlores is found here.

show abstract

“…The behavior of these materials has been attributed to "moment fragmentation" [25]: a theoretically proposed magnetic state with a crystallized lattice of magnetic monopoles, forming a three-in-one-out order on a pyrochlore lattice [17,[34][35][36]. However, despite much use of the fragmentation language [20,31], the three-in-one-out order is absent from these materials and thus it is not the ground state but the excitations which are considered fragmented [37].…”

Section: Introductionmentioning

confidence: 99%

Beyond magnons in Nd2ScNbO7: An Ising pyrochlore antiferromagnet with all in all out order and random fields

Scheie,

Sanders,

Qiu

et al. 2021

Preprint

View full text Add to dashboard Cite

We report the low temperature magnetic properties of Nd 3+ pyrochlore Nd2ScNbO7. Susceptibility and magnetization show an easy-axis moment, and heat capacity reveals a phase transition to long range order at TN = 371(2) mK with a fully recovered ∆S = R ln(2), 53% of it recovered for T > TN . Elastic neutron scattering shows a long-range all-in-all-out magnetic order with low-Q diffuse elastic scattering. Inelastic neutron scattering shows a low-energy flat-band, indicating a magnetic Hamiltonian similar to Nd2Zr2O7. Nuclear hyperfine excitations measured by ultra-highresolution neutron backscattering indicates a distribution of static electronic moments below TN , which may be due to B-site disorder influencing Nd crystal electric fields. Analysis of heat capacity data shows an unexpected T -linear or T 3/2 term which is inconsistent with conventional magnon quasiparticles, but is consistent with fractionalized spinons or gapless local spin excitations. We use legacy data to show similar behavior in Nd2Zr2O7. Comparing local static moments also reveals a suppression of the nuclear Schottky anomaly in temperature, evidencing a fraction of Nd sites with nearly zero static moment, consistent with exchange-disorder-induced random singlet formation. Taken together, these measurements suggest an unusual fluctuating magnetic ground state which mimics a spin-liquid-but may not actually be one.

show abstract

Fragmentation in Frustrated Magnets: A Review

Cited by 29 publications

References 133 publications

Dynamical Axions in $U(1)$ Quantum Spin Liquids

Dynamical Axions in $U(1)$ Quantum Spin Liquids

Absence of moment fragmentation in the mixed B -site pyrochlore Nd2GaSbO7

Beyond magnons in Nd2ScNbO7: An Ising pyrochlore antiferromagnet with all in all out order and random fields

Contact Info

Product

Resources

About