Scattering of Raman phonons on magnetic and electronic excitations in the pyrochlores Nd 2 Zr 2 O 7 and Nd 2 Ir 2 O 7

Magnetic rare earth atoms on pyrochlore lattices can produce exotic magnetic states such as spin ice and quantum spin ice. These states are a result of the frustration in the pyrochlore lattice, as well as crystal field degrees of freedom of rare earth atoms, and their interactions with the lattice. Raman scattering spectroscopy, which possesses high spectral resolution and can easily access broad energy and temperature ranges, is an optimal tool to study these excitations and their interactions. In this work we follow the Raman scattering of zone center phonons and crystal field excitations of ${\mathrm{Nd}}^{3+}$ in ${\mathrm{Nd}}_{2}{\mathrm{Zr}}_{2}{\mathrm{O}}_{7}$ and ${\mathrm{Nd}}_{2}{\mathrm{Ir}}_{2}{\mathrm{O}}_{7}$ in the temperature range where these materials are paramagnetic. A comparison between an insulating ${\mathrm{Nd}}_{2}{\mathrm{Zr}}_{2}{\mathrm{O}}_{7}$ and a semimetallic ${\mathrm{Nd}}_{2}{\mathrm{Ir}}_{2}{\mathrm{O}}_{7}$ allows us to distinguish between scattering of phonons on other phonons, crystal field excitations, and electrons, highlighting interactions between these degrees of freedom.