Thermodynamics of the dipole-octupole pyrochlore magnet Ce${}_2$Hf${}_2$O${}_7$ in applied magnetic fields

Abstract

The recently discovered dipole-octupole pyrochlore magnet Ce${}_2$Hf${}_2$O${}_7$ is a promising three-dimensional quantum spin liquid candidate which shows no signs of ordering at low temperature. The low energy effective pseudospin-1/2 description in a magnetic field is characterized by the XYZ Hamiltonian and a Zeeman term where the dipolar local $z$-component of the pseudospin couples to the local $z$-component of the applied magnetic field, while the local $x$- and $y$-components of the pseudospin remain decoupled as a consequence of their octupolar character. Using effective Hamiltonian parameters determined in V. Poree et al., arXiv:2305.08261 (2023), remarkable experimental features can be reproduced, as for instance the specific heat and magnetization data as well as the continuum of states seen in neutron scattering. Here we investigate the thermodynamic response to magnetic fields applied along the global [110] direction using specific heat measurements and fits using numerical methods, and solve the corresponding magnetic structure using neutron diffraction. Specific heat data in moderate fields are reproduced well, however, at high fields the agreement is not satisfactory. We especially observe a two-step release of entropy, a finding that demands a review of both theory and experiment. We address it within the framework of three possible scenarios, including an analysis of the crystal field Hamiltonian not restricted to the two-dimensional single-ion doublet subspace. We conclusively rule out two of these scenarios and find qualitative agreement with a simple model of field misalignment with respect to the crystalline direction. We discuss the implications of our findings for [111] applied fields and for future experiments on Ce${}_2$Hf${}_2$O${}_7$ and its sister compounds.

16 pages, 13 figures. v2 closely matches the published version

References in corpus (15)

• Pyrochlore Photons: The U(1) Spin Liquid in a S=1/2 Three-Dimensional Frustrated Magnet
• Dirac Strings and Magnetic Monopoles in Spin Ice Dy2Ti2O7
• Physical realization of a quantum spin liquid based on a novel frustration mechanism
• The planar thermal Hall conductivity in the Kitaev magnet α-RuCl3
• Quantum Spin Ice Dynamics in the Dipole-Octupole Pyrochlore Magnet Ce${}_2$Zr${}_2$O${}_7$
• Is the Yb2Ti2O7 pyrochlore a quantum spin ice?
• Disordered Route to the Coulomb Quantum Spin Liquid: Random Transverse Fields on Spin Ice in Pr${}_2$Zr${}_2$O${}_7$
• Symmetry Enriched U(1) Topological Orders for Dipole-Octupole Doublets on a Pyrochlore Lattice
• Antiferro-quadrupolar correlations in the quantum spin ice candidate Pr2Zr2O7
• Physical properties of a candidate quantum spin-ice system Pr2Hf2O7
• Low energy structure of spiral spin liquids
• Crystal-field states and defect levels in candidate quantum spin ice Ce${}_2$Hf${}_2$O${}_7$
• Dipolar spin ice regime proximate to an all-in-all-out Néel ground state in the dipolar-octupolar pyrochlore Ce${}_2$Sn${}_2$O${}_7$
• Quantum Spin Ice Response to a Magnetic Field in the Dipole-Octupole Pyrochlore Ce${}_2$Zr${}_2$O${}_7$
• Magnetic Field Response of Dipolar-Octupolar Quantum Spin Ice

Cited by in corpus (4)

• Dipolar-octupolar correlations and hierarchy of exchange interactions in Ce${}_2$Hf${}_2$O${}_7$
• Two-Peak Heat Capacity Accounts for $R\ln (2)$ Entropy and Ground State Access in the Dipole-Octupole Pyrochlore Ce${}_2$Hf${}_2$O${}_7$
• Spinon band flattening by its emergent gauge field in quantum kagome ice
• Towards a global phase diagram of Ce-based dipolar-octupolar pyrochlore magnets under magnetic fields