The exotic properties of multipolar quantum spin ice candidate Pr₂Zr₂O₇ are determined
by the coupling of spin, orbital, and lattice degrees of freedom [1]. Some of these interactions
can be followed through the line shape of crystal field excitations which are detected
by high resolution spectroscopy. Using Raman scattering spectroscopy we explore crystal
field excitations spectra of Pr³⁺ as a function of temperature down to 2 K, and as a
function of magnetic field applied in [100] and [111] directions. We demonstrate vibronic
interactions of crystal field levels of Pr³⁺ with phonons, prominent for excited states. We
identify an unconventional temperature behavior of a splitting of the Pr³⁺ non-Kramers
ground state doublet and suggest a static or dynamic deviation of Pr³⁺ from the ideal
position as the origin of the effect.
In magnetic field H ∥ [100] crystal field excitations spectra can be fully understood
within conventional Zeeman splitting. With magnetic field applied in H ∥ [111] direction,
magnetic moments of pyrochlores are known to split into triangular lattice planes of
moments aligned with the field and Kagome planes which can show Kagome ice behavior
[2]. We demonstrate that Zeeman splitting can explain only the crystal field spectra of
the moments aligned parallel to the [111] magnetic field. Crystal field spectra of Kagome
planes show evidence of fluctuations, without reaching a polarized state in magnetic field
up to H=14 T.