[Seminar] "Experimental signatures of quantumness in rare-earth pyrochlores" by Dr. Romain Sibille
Dr. Romain Sibille from Paul Scherrer Institute
Magnetic systems with competing interactions often adopt exotic ground states, which can be relevant to study new physics in quantum matter. A recurrent ingredient to stabilize such phases is geometrical frustration, such as in pyrochlore oxides where rare-earth magnetic moments decorate a lattice of corner-sharing tetrahedra. An unusual spin liquid appears for example in the pyrochlore Ho2Ti2O7, which features a classical ‘spin ice’ short-range correlated state. A local constraint – the 2-in-2-out ‘ice rule’ acting on each tetrahedron – leads to a manifold of degenerate ground states in which the spin correlations give rise to emergent magnetostatics. Spin flips violating the ice rule generate magnetic monopole excitations, a mobile magnetic charge regarded as a quasiparticle carrying half of the dipole moment. A quantum analogue of the spin ice state is predicted to be a special type of quantum spin liquid formed through the coherent superposition of spin ice configurations. Remarkably, the low-energy physics of this quantum spin ice state is predicted to be a lattice analogue of quantum electrodynamics. I present recent experimental results showing signatures of quantum spin liquid states in different rare-earth pyrochlore oxides.