Spin dynamics in the ordered spin ice Tb$_2$Sn$_2$O$_7$

TL;DR

This study uses advanced inelastic neutron scattering to explore the spin dynamics of ordered spin ice Tb$_2$Sn$_2$O$_7$, revealing the need for a new interaction involving spin-lattice coupling to explain the observations.

Contribution

It introduces evidence for a novel spin-lattice interaction mechanism in ordered spin ice Tb$_2$Sn$_2$O$_7$ based on high-resolution neutron scattering data.

Findings

Identification of a new spin-lattice coupling interaction.

Observation of a low-temperature distortion affecting crystal field levels.

Necessity of including this interaction to explain experimental data.

Abstract

Geometrical frustration is a central challenge in contemporary condensed matter physics, a crucible favourable to the emergence of novel physics. The pyrochlore magnets, with rare earth magnetic moments localized at the vertices of corner-sharing tetrahedra, play a prominent role in this field, with a rich variety of exotic ground states ranging from the "spin ices" \hoti\ and \dyti\ to the "spin liquid" and "ordered spin ice" ground states in \tbti\ and \tbsn. Inelastic neutron scattering provides valuable information for understanding the nature of these ground states, shedding light on the crystal electric field (CEF) level scheme and on the interactions between magnetic moments. We have performed such measurements with unprecedented neutron flux and energy resolution, in the "ordered spin ice" \tbsn. We argue that a new interaction, which involves the spin lattice coupling through a low temperature distortion of the trigonal crystal field, is necessary to account for the data.