Exotic magnetisation plateaus in a quasi-2D Shastry-Sutherland model

TL;DR

This paper uncovers unconventional magnetization plateaus in a quasi-2D Shastry-Sutherland model, revealing complex entangled states stabilized by correlated hopping, with implications for understanding frustrated quantum magnets like SrCu(BO_3)_2.

Contribution

It introduces a novel quasi-2D model exhibiting unique magnetization plateaus stabilized by correlated hopping, analyzed through advanced numerical methods.

Findings

Magnetization plateaus at M=1/8, 3/16, 1/4, 1/2 identified

Plateaus exhibit highly entangled and classical structures

Correlated hopping crucial for plateau stabilization

Abstract

We find unconventional Mott insulators in a quasi-2D version of the Shastry-Sutherland model in a magnetic field. In our realization on a 4-leg tube geometry, these are stabilized by correlated hopping of localized magnetic excitations. Using perturbative continuous unitary transformations (pCUTs, plus classical approximation or exact diagonalization) and the density matrix renormalisation group method (DMRG), we identify prominent magnetization plateaus at magnetizations M=1/8, M=3/16, M=1/4, and M=1/2. While the plateau at M=1/4 can be understood in a semi-classical fashion in terms of diagonal stripes, the plateau at M=1/8 displays highly entangled wheels in the transverse direction of the tube. Finally, the M=3/16 plateau is most likely to be viewed as a classical 1/8 structure on which additional triplets are fully delocalized around the tube. The classical approximation of the effective model fails to describe all these plateau structures which benefit from correlated hopping. We relate our findings to the full 2D system, which is the underlying model for the frustrated quantum magnet SrCu(BO_3)_2.