Journal article

Cu-Sb dumbbell arrangement in the spin-orbital liquid candidate Ba3CuSb2O9

The absence of both spin freezing and of a static Jahn-Teller effect have led to the proposition that Ba3CuSb2O9 is a quantum spin-orbital liquid. However, theoretical understanding of the microscopic origin of this behavior has been hampered by a lack of consensus on the lattice structure. Cu ions have been proposed to realize either a triangular lattice, a short-range ordered honeycomb lattice, or a disordered lattice with stripelike correlations. Here we analyze the stability of idealized versions of these arrangements using density functional theory. We find stripe order of Cu ions to be energetically favored, hinting towards stripelike local Cu-Cu arrangements, while long-range order is presumably hindered due to disorder effects. Furthermore, we find evidence of significant interlayer interactions between Cu-Sb dumbbells, which affects the out-of-plane arrangement. Analysis of the relaxed crystal structures, electronic properties, and tight-binding parameters provides clues as to the nature of the Jahn-Teller distortions.


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