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

Published

September 7, 2021

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. A. 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 C_p 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 C_p and a low temperature form for C_p that is consistent with both the calculated near-neighbour exchange parameters and a T³ C_p appropriate for emergent gapless photons. This low temperature form for C_p allows for R ln(2) entropy to be accounted for up to T = 10 K. Phenomenologically, the entropy recovery above the plateau in C_p, near T = 0.08 K, gives R ln(2) less R/2/ ln(3/2), the missing Pauling, spin ice entropy.

Citation

arXiv

Pub Type

Journals

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. (2021), The case for a U(1)_π Quantum Spin Liquid Ground State in the Dipole-Octupole Pyrochlore Ce₂Zr₂O₇, arXiv (Accessed April 19, 2024)