Ground states of an Ising model on an extended Shastry-Sutherland lattice and the 1/2-magnetization plateau in some rare-earth-metal tetraborides

TL;DR

This paper provides a complete theoretical solution for the ground states of an extended Ising model on a Shastry-Sutherland lattice, explaining the origin of the 1/2-magnetization plateau observed in certain rare-earth tetraborides.

Contribution

It introduces a rigorous proof that additional diagonal interactions induce the 1/2-magnetization plateau in the model, clarifying its physical origin in rare-earth tetraborides.

Findings

Proves the interaction causes the 1/2-magnetization plateau.

Explains the plateau's emergence in ErB4 and TmB4.

Provides a complete ground-state solution for the extended model.

Abstract

A complete solution of the ground-state problem for an Ising model on the Shastry-Sutherland lattice with an additional interaction along the diagonals of "empty" squares in an applied magnetic field is presented. A rigorous proof is given that this interaction gives rise to a plateau at one-half of the saturation magnetization. Such a fractional plateau has been observed in some rare-earth-metal tetraborides, in particular, in strong Ising magnets ErB4 (where it is the only one) and TmB4 (where it is the broadest one), but its origin has remained unclear. Our study sheds new light on the solution of this problem.