NMR evidence for the persistence of spin-superlattice above the 1/8 magnetization plateau in SrCu2(BO3)2

TL;DR

This study uses 11B NMR to investigate the spin structure of SrCu2(BO3)2 around the 1/8 magnetization plateau, revealing a persistent spin-superlattice above the plateau that suggests a complex supersolid-like phase.

Contribution

First NMR evidence showing the persistence of spin-superlattice structure above the 1/8 plateau in SrCu2(BO3)2, indicating a complex phase beyond simple melting.

Findings

Spin-superlattice persists above the 1/8 plateau.

The phase above the plateau is more complex than a simple melt.

Evidence suggests a supersolid-like phase with complex microscopic nature.

Abstract

We present 11B NMR studies of the 2D frustrated dimer spin system SrCu2(BO3)2 in the field range 27-31 T covering the upper phase boundary of the 1/8 magnetization plateau, identified at 28.4 T. Our data provide a clear evidence that above 28.4 T the spin-superlattice of the 1/8 plateau is modified but does not melt even though the magnetization increases. Although this is precisely what is expected for a supersolid phase, the microscopic nature of this new phase is much more complex. We discuss the field-temperature phase diagram on the basis of our NMR data.