Exploring mixed Dipole-Octupole correlations in Ce-Based Quantum Spin Ice candidates

The theoretical study of highly frustrated magnetic systems has led to the identification of exotic phases exhibiting disordered yet highly entangled ground states from which emergent fractionalized excitations can arise. These so-called quantum spin liquids (QSLs) [1] are, however, notoriously difficult to experimentally identify due to the lack of a definitive experimental signature. Recently, cerium-based pyrochlore oxides have attracted significant attention as potential realizations of three-dimensional QSLs known as Quantum Spin Ices (QSIs) [2].

The three reported compounds, namely Ce₂Sn₂O₇ [3], Ce₂Zr₂O₇ [4,5], and Ce₂Hf₂O₇ [6], have been shown to stabilize a Ce³⁺ single-ion ground state doublet of mixed dipolar-octupolar nature, exhibit no long-range magnetic order, and feature continua of low-energy excitations interpreted as the spinons of a QSI. However, the exact nature of their respective magnetic ground state remains an open question, owing to the several possible phases dominated by either dipolar or octupolar degrees of freedom with distinct associated observables [7-9].

To gain deeper insights into these elusive states of matter, low-temperature thermodynamic measurements and neutron scattering have proven essential tools, particularly when paired with ever-improving theoretical models and predictions [7-11]. In this presentation, I will show how this synergy between theory and experiment is advancing our understanding of cerium-based QSI candidates, helping to rationalize their sometimes contrasting behaviors in terms of their respective magnetic correlations.

[1] L. Balents, Nature 464, 199 (2010).

[2] M. J. P. Gingras and P. A. McClarty, Reports on Progress in Physics 77, 056501 (2014).

[3] R. Sibille et al., Nature Physics 16, 546 (2020).

[4] J. Gaudet et al., Phys. Rev. Lett. 122, 187201 (2019).

[5] B. Gao, et al., Nature Phys. 15, 1052–1057 (2019).

[6] V. Porée et al., Phys. Rev. Mater. 6, 044406 (2022).

[7] A. Bhardwaj et al., npj Quantum Materials 7 (2022).

[8] B. Placke, R. Moessner, and O. Benton, Phys. Rev. B 102, 245102 (2020).

[9] F. Desrochers & Y. B. Kim, Phys. Rev. Lett. 132, 066502 (2024).

[10] M. Udagawa & R. Moessner, Phys. Rev. Lett. 122, 117201 (2019).

[11] S.D. Morampudi, F. Wilczek & C.R. Laumann, Phys. Rev. Lett. 124, 097204 (2020).