Kate Ross

Quantum Excitations in Quantum Spin Ice

Recent work has highlighted remarkable effects of classical thermal fluctuations in the dipolar spin ice compounds, such as ‘‘artificial magnetostatics,’’ manifesting as Coulombic power-law spin correlations and particles behaving as diffusive ‘‘magnetic monopoles.’’ In this paper, we address quantum spin ice, giving a unifying framework for the study of magnetism of a large class of magnetic compounds with the pyrochlore structure, and, in particular, discuss Yb2Ti2O7, and extract its full set of Hamiltonian parameters from high-field inelastic neutron scattering experiments. We show that fluctuations in Yb2Ti2O7 are strong, and that the Hamiltonian may support a Coulombic ‘‘quantum spin liquid’’ ground state in low magnetic fields and host an unusual quantum critical point at larger fields. This appears consistent with puzzling features seen in prior experiments on Yb2Ti2O7. Thus, Yb2Ti2O7 is the first quantum spin liquid candidate for which the Hamiltonian is quantitatively known.

Order by Quantum Disorder in Er2Ti2O7

Here we establish the systematic existence of a U(1) degeneracy of all symmetry-allowed Hamiltonians quadratic in the spins on the pyrochlore lattice, at the mean-field level. By extracting the Hamiltonian of Er(2)Ti(2)O(7) from inelastic neutron scattering measurements, we then show that the U(1)-degenerate states of Er(2)Ti(2)O(7) are its classical ground states, and unambiguously show that quantum fluctuations break the degeneracy in a way which is confirmed by experiment. The degree of symmetry protection of the classical U(1) degeneracy in Er(2)Ti(2)O(7) is unprecedented in other materials. As a consequence, our observation of order by disorder is unusually definitive. We provide further verifiable consequences of this phenomenon, and several additional comparisons between theory and experiment.

Unconventional Magnetic Ground State in Yb2Ti2O7

We report low temperature specific heat and muon spin relaxation/rotation (

Low-energy electrodynamics of novel spin excitations in the quantum spin ice Yb 2 Ti 2 O 7

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A measure of monopole inertia in the quantum spin ice Yb2Ti2O7

SR) measurements on both polycrystalline and single crystal samples of the pyrochlore magnet Yb

Static and dynamic X Y -like short-range order in a frustrated magnet with exchange disorder

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Ground state selection under pressure in the quantum pyrochlore magnet Yb 2 Ti 2 O 7

Ti

Time-resolved one-dimensional detection of x-ray scattering in pulsed magnetic fields.

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Low frequency spin dynamics in XY quantum spin ice Yb

O

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