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.

[1]  Daisuke Nakajima,et al.  Chemical and orbital fluctuations in Ba 3 CuSb 2 O 9 , 2016 .

[2]  R. Valentí,et al.  Challenges in design of Kitaev materials: Magnetic interactions from competing energy scales , 2016, 1603.02548.

[3]  F. Mila,et al.  Topological Aspects of Symmetry Breaking in Triangular-Lattice Ising Antiferromagnets. , 2016, Physical review letters.

[4]  R. Valentí,et al.  Monoclinic crystal structure of α − RuCl 3 and the zigzag antiferromagnetic ground state , 2015, 1509.02670.

[5]  F. Mila,et al.  Disorder-Driven Spin-Orbital Liquid Behavior in the Ba3XSb2O9 Materials. , 2015, Physical review letters.

[6]  F. Mila,et al.  Exploring the spin-orbital ground state of Ba 3 CuSb 2 O 9 , 2014, 1406.7605.

[7]  S. Ishihara,et al.  Absence of Jahn−Teller transition in the hexagonal Ba3CuSb2O9 single crystal , 2014, Proceedings of the National Academy of Sciences.

[8]  H. Takagi,et al.  Hyperhoneycomb Iridate β-Li2IrO3 as a platform for Kitaev magnetism. , 2014, Physical review letters.

[9]  K. V. Shanavas,et al.  Electronic structure ofBa3CuSb2O9: A candidate quantum spin liquid compound , 2014 .

[10]  T. Smidt,et al.  Realization of a three-dimensional spin–anisotropic harmonic honeycomb iridate , 2014, Nature Communications.

[11]  A. Baron,et al.  Dynamical spin–orbital correlation in the frustrated magnet Ba3CuSb2O9 , 2013, Nature Communications.

[12]  P. Mendels,et al.  Singlet ground state of the quantum antiferromagnet Ba(3)CuSb(2)O(9). , 2012, Physical review letters.

[13]  F. Mila,et al.  28pAK-16 Spin-Orbital Quantum Liquid on the Honeycomb Lattice , 2012, 1207.6029.

[14]  S. Ishihara,et al.  Dynamical Jahn-Teller effect in a spin-orbital coupled system , 2012, 1209.0239.

[15]  G. Jackeli,et al.  Mott insulators in the strong spin-orbit coupling limit: from Heisenberg to a quantum compass and Kitaev models. , 2008, Physical review letters.

[16]  S. Korshunov.  Nature of phase transitions in the striped phase of a triangular-lattice Ising antiferromagnet , 2005, cond-mat/0506722.

[17]  Y. Shimizu,et al.  Spin liquid state in an organic Mott insulator with a triangular lattice. , 2003, Physical review letters.

[18]  G. Scuseria,et al.  Hybrid functionals based on a screened Coulomb potential , 2003 .

[19]  D. Khomskii,et al.  Orbital ordering and frustrations , 2003, cond-mat/0304089.

[20]  G. Khaliullin,et al.  Orbital liquid in three-dimensional mott insulator: LaTiO3 , 2000, Physical review letters.

[21]  Helmut Eschrig,et al.  FULL-POTENTIAL NONORTHOGONAL LOCAL-ORBITAL MINIMUM-BASIS BAND-STRUCTURE SCHEME , 1999 .

[22]  C. Humphreys,et al.  Electron-energy-loss spectra and the structural stability of nickel oxide: An LSDA+U study , 1998 .

[23]  Kresse,et al.  Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. , 1996, Physical review. B, Condensed matter.

[24]  N. Nagaosa,et al.  Orbital liquid in perovskite transition-metal oxides , 1996, cond-mat/9606160.

[25]  Hafner,et al.  Ab initio molecular dynamics for liquid metals. , 1995, Physical review. B, Condensed matter.

[26]  Henk W. J. Blöte,et al.  Triangular SOS models and cubic-crystal shapes , 1984 .

[27]  L. Balicas,et al.  Spin Liquid State in the S=1/2 Triangular Lattice Ba_{3}CuSb_{2}O_{9} , 2014 .

[28]  R. Deblock,et al.  Observation of the Orbital Quantum Dynamics in the Spin-1 / 2 Hexagonal Antiferromagnet Ba 3 CuSb 2 O 9 , 2022 .