Importance of dynamic lattice effects for crystal field excitations in the quantum spin ice candidate Pr2Zr2O7

Phonon spectrum of Pr$_2$Zr$_2$O$_7$ and Pr$_2$Ir$_2$O$_7$ as an evidence of coupling of the lattice with electronic and magnetic degrees of freedom

“…This spectral range covers all Raman-active phonons and excitations except the lowest excited state at about 80 cm −1 discussed in Ref. [17]. Due to the similarities of the crystal structure, many of the observed excitations show similar energies in these two compounds, however the Raman response of Pr 2 Ir 2 O 7 is approximately two orders of magnitude weaker than that of Pr 2 Zr 2 O 7 , due to the fact that the first material is metallic.…”

“…The screening present in the metallic state also affects the relative intensity of the phonons and CEF excitations. For the latter, in Pr 2 Ir 2 O 7 spectra we observe only the CEF exitation at around 460 cm −1 , which is coupled to phonons by a vibronic coupling process [17].…”

“…Moreover, at room temperature the phonon appears as an antiresonance in the broad band of CEF A 1g → E g transition, which is an evidence of an interaction of the phonon with this transition [31]. The observed spectroscopic effect is very different from vibronic effects on mixing of CEF and phonons, discussed in [17,32].…”

“…1. The low temperature data allows to resolve not only phonon excitations, but also crystal electric field (CEF) which can be observed only at low temperatures [17]. This spectral range covers all Raman-active phonons and excitations except the lowest excited state at about 80 cm −1 discussed in Ref.…”

“…CEF excitations of Pr 3+ (marked green) were assigned based on the neutron scattering results for these two materials [18][19][20] and are discussed in Ref. [17]. Additionally, in the spectra of Pr 2 Ir 2 O 7 we observe electronic excitations at around 250 cm −1 (marked yellow) and excitations typical for iridates at around 650 cm −1 (marked blue) [21].…”