Spontaneous structural distortion of metallic Shastry-Sutherland system DyB4 by quadrupole-spin-lattice coupling

TL;DR

This study reveals how quadrupole-spin-lattice coupling induces spontaneous structural distortion in DyB4, alleviating frustration in its Shastry-Sutherland lattice through experimental structural analysis.

Contribution

It provides the first detailed structural characterization of DyB4 across phase transitions, demonstrating how quadrupole-spin-lattice coupling lifts geometric frustration.

Findings

Structural modifications at quadrupolar transition relieve frustration.

Quadrupole-spin-lattice coupling induces spontaneous distortion.

Spin-orbit and RKKY interactions influence behavior.

Abstract

DyB4 has a two-dimensional Shastry-Sutherland (Sh-S) lattice with strong Ising character of the Dy ions. Despite the intrinsic frustrations, surprisingly, it undergoes two successive transitions: a magnetic ordering at TN = 20K, and a quadrupole ordering at TQ=12.5 K. From high-resolution neutron and synchrotron X-ray powder diffraction studies, we have obtained full structural information on this material in all phases, and demonstrate that structural modifications occurring at quadrupolar transition lead to the lifting of frustrations inherent in the Sh-S model. Our study thus provides a complete experimental picture of how the intrinsic frustration of the Sh-S lattice can be lifted by the coupling to quadrupole moments. We show that two other factors, i.e. strong spin-orbit coupling and long-range RKKY interaction in metallic DyB4, play an important role in this behavior.