| Spin ice is a magnetic analog of H2O ice that harbors dense static disorder. Dipolar interactions between classical spins yield a frozen frustrated state with residual configurational Pauling entropy and emergent magnetic monopolar quasiparticles. Introducing quantum fluctuations is of great interest as this could melt spin ice and allow coherent propagation of monopoles. Here, we report experimental evidence for quantum dynamics of magnetic monopolar quasiparticles in Pr based pyrochlore compounds, Pr2T2O7. In the insulating Pr2Zr2O7, we found >90% of the neutron scattering is inelastic and devoid of pinch points furnishing evidence for magnetic monopolar quantum fluctuations. On the other hand, the metallic Pr2Ir2O7 exhibits a putative chiral spin liquid state, with strong non-Fermi liquid properties, suggesting the release of Pauling entropy due to quantum dynamics. This work is based on the collaboration with Kenta Kimura, Jun J. Ishikawa, Yo Machida, Collin Broholm, Jiajia Wen, Yoshi Tokiwa, Philipp Gegenwart, Hiroshi Sawa, Eiji Nishibori, Toshiro Sakakibara, Yasuyuki Shimura. |
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