Partial Kondo Screening Solves the Mystery of Rare Earth Tetraborides

Abstract

We invoke a new mechanism to account for multiple magnetization plateaus observed in rare-earth tetraborides. Using a combination of hybrid and semiclassical Monte Carlo simulations of the Kondo lattice model (KLM) on the Shastry-Sutherland lattice (SSL), we find robust magnetization plateaus at fractions 1/6, 2/9, 1/4, 1/3, 1/2, 2/3 and 3/4 of the saturation magnetization. We find that most of the plateau states are partially Kondo screened and emerge from the field-tuning of a complex three-way competition between the kinetic energy, the Kondo coupling, and the magnetic frustration. Most remarkably, the unusual magneto-transport reported in ErB$_4$ and TmB$_4$ admits an unexpectedly simple explanation within our mechanism. This work not only provides an elegant and simple solution to the long-standing puzzle of metamagnetism and anomalous magnetotransport in RB$_4$, but also introduces a novel mechanism to predict and discover new correlated phases in frustrated Kondo lattices.