Magnetoelastically induced vibronic bound state in the spin-ice pyrochlore Ho2Ti2 O7

J. Gaudet, A. M. Hallas, C. R.C. Buhariwalla, G. Sala, M. B. Stone, M. Tachibana, K. Baroudi, R. J. Cava, B. D. Gaulin

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6 Scopus citations

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 languageEnglish (US)
Article number014419
JournalPhysical Review B
Volume98
Issue number1
DOIs
StatePublished - Jul 19 2018

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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