Quantum dynamics and emergent unconventional phase in Yb2Ti2O7

Résumé :

Yb2Ti2O7 is a classic and well-studied pyrochlore magnet, but it continues to hold surprises for science. In this talk I present inelastic neutron scattering showing the low-field evolution of the spectrum from diffuse continua to sharp excitations. I compare this to several theoretical models which capture its behavior to varying degrees, but which fail in the zero-field phase–which our exact diagonalization calculations show to be an emergent quantum disordered phase between ferromagnetism and antiferromagnetism. Much of the behavior matches the phenomenology of quantum criticality: dimensional reduction, flat bands collapsing to zero frequency, and an emergent quantum phase on the boundary between competing phases. Thus although Yb2Ti2O7 is not a quantum spin ice, it appears to be dominated by intrinsic, emergent non-magnon fluctuations from an unconventional quantum phase.

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Contact : andrew.fefferman@neel.cnrs.fr