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The case for a U(1)π Quantum Spin Liquid Ground State in the Dipole-Octupole Pyrochlore Ce2Zr2O7

Published

Author(s)

E. Smith, O. Benton, D. Yahne, B. Placke, Jonathan Gaudet, J. Dudemaine, A. Fitterman, J. Beare, A. Wildes, S. Bhattacharya, T. DeLazzer, C.R.C. Buhariwalla, Nicholas Butch, R. Movshovich, J. Garrett, C. Marjerrison, J. Clancy, E. Kermarrec, G. Luke, A. Bianchi, K. Ross, B. Gaulin

Abstract

The Ce3+ pseudospin-1/2 degrees of freedom in the pyrochlore magnet Ce2Zr2O7 are known to possess dipole-octupole (DO) character, making it a candidate for novel quantum spin liquid (QSL) ground states at low temperatures. We report new heat capacity (Cp) measurements on Ce2Zr2O7 which rise sharply at low temperatures, initially plateauing near 0.08 K, before falling off towards a high temperature zero beyond 3 K. Above ∼0.5 K, the Cp data set can be fit to the results of a quantum numerical linked cluster (NLC) calculation, that allows estimates for the terms in the XYZ Hamiltonian expected for such DO pyrochlore systems. Fits of the same theory to the temperature dependence of neutron scattering and magnetic susceptibility complement this analysis to produce robust estimates of the exchange parameters. Polarized neutron diffraction results show spin-flip scattering with pinch points, largely consistent with predictions from the NLC calculation. However, the non-spin flip structure factor shows zone-boundary scattering similar to that observed in the dipolar spin ice Ho2Ti2O7 and likely arising from long-range dipolar interactions. We conclude that Ce2Zr2O7 realizes a U(1)π QSL state at low temperatures, and one that resides near the boundary between dipolar and octupolar character. We then interpolate between the NLC-calculated T > ∼0.5 K Cp and a low temperature form for Cp that is consistent with both the calculated near-neighbour exchange parameters and a T3 Cp appropriate for emergent gapless photons. This low temperature form for Cp allows for R ln(2) entropy to be accounted for up to T = 10 K. Phenomenologically, the entropy recovery above the plateau in Cp, near T = 0.08 K, gives R ln(2) less R/2/ ln(3/2), the missing Pauling, spin ice entropy.
Citation
Physical Review X

Keywords

quantum spin liquid, pyrochlore, neutron scattering

Citation

Smith, E. , Benton, O. , Yahne, D. , Placke, B. , Gaudet, J. , Dudemaine, J. , Fitterman, A. , Beare, J. , Wildes, A. , Bhattacharya, S. , DeLazzer, T. , Buhariwalla, C. , Butch, N. , Movshovich, R. , Garrett, J. , Marjerrison, C. , Clancy, J. , Kermarrec, E. , Luke, G. , Bianchi, A. , Ross, K. and Gaulin, B. (2022), The case for a U(1)<sub>&#960;</sub> Quantum Spin Liquid Ground State in the Dipole-Octupole Pyrochlore Ce<sub>2</sub>Zr<sub>2</sub>O<sub>7</sub>, Physical Review X (Accessed June 29, 2022)
Created April 13, 2022