Abstract
The single-ion physics of Ho2Ti2O7 is well understood to produce strong Ising anisotropy, which is an essential ingredient to its low-temperature spin-ice state. We present inelastic neutron scattering measurements on Ho2Ti2O7 that reveal a clear inconsistency with its established single-ion Hamiltonian. Specifically, we show that a crystal-field doublet near 60 meV is split by approximately 3 meV. Furthermore, this crystal-field splitting is not isolated to Ho2Ti2O7 but can also be found in its chemical pressure analogs Ho2Ge2O7 and Ho2Sn2O7. We demonstrate that the origin of this effect is a vibronic bound state, resulting from the entanglement of a phonon and crystal-field excitation. We derive the microscopic Hamiltonian that describes the magnetoelastic coupling and provides a quantitative description of the inelastic neutron spectra.
| Original language | English |
|---|---|
| Article number | 014419 |
| Journal | Physical Review B |
| Volume | 98 |
| Issue number | 1 |
| DOIs | |
| State | Published - Jul 19 2018 |
Funding
This research at ORNL's Spallation Neutron Source was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, US Department of Energy. This work was supported by the Natural Sciences and Engineering Research Council of Canada. The sample growth at Princeton University was supported by the US Department of Energy, Basic Energy Sciences, through the IQM at Johns Hopkins University, Grant No. DE-FG02-98-ER46544.