Charge and spin order on the triangular lattice -- Na${}_x$CoO${}_2$ at $x=0.5$

Abstract

The nature of electronic states due to strong correlation and geometric frustration on the triangular lattice is investigated in connection to the unconventional insulating state of Na${}_x$CoO${}_2$ at $x=0.5$. We study an extended Hubbard model using a spatially unrestricted Gutzwiller approximation. We find a new class of charge and spin ordered states at $x=1/3$ and $x=0.5$ where antiferromagnetic (AF) frustration is alleviated via weak charge inhomogeneity. At $x=0.5$, we show that the $\sqrt{3}a\times 2a$ off-plane Na dopant order induces weak $\sqrt{3}a\times 1a$ charge order in the Co layer. The symmetry breaking enables successive $\sqrt{3}a\times 1a$ AF and $2a\times 2a$ charge/spin ordering transitions at low temperatures. The Fermi surface is truncated by the $2a\times 2a$ hexagonal zone boundary into small electron and hole pockets. We study the phase structure and compare to recent experiments.

4 pages, 4 figures, revtex4 file

References in corpus (10)

• Fermi surface and quasiparticle dynamics of Na(x)CoO2 {x=0.7} investigated by Angle-Resolved Photoemission Spectroscopy
• Fermi surface evolution and Luttinger theorem in Na${}_x$CoO${}_2$: a systematic photoemission study
• ARPES on Na${}_{0.6}$CoO${}_2$: Fermi surface, extended flat dispersion, and unusual band splitting
• Electron correlation and Fermi surface topology of Na${}_x$CoO${}_2$
• Novel Charge Order and Superconductivity in Two-Dimensional Frustrated Lattice at Quarter Filling
• Quasiparticle coherence and the nature of the metal-insulator phase transition in Na${}_x$CoO${}_2$
• Disproportionation Transition at Critical Interaction Strength: Na${}_{1/2}$CoO${}_2$
• Charge order and superconductivity in a two-dimensional triangular lattice at n=2/3
• Destruction of the small Fermi surfaces in Na${}_x$CoO${}_2$ by Na disorder
• Shubnikov de Haas effect in the metallic state of Na${}_{0.3}$CoO${}_2$

Cited by in corpus (13)

• Searching for Stable Na-ordered Phases in Single Crystal Samples of gamma-NaxCoO2
• Nodal $d+id$ pairing and topological phases on the triangular lattice: unconventional superconducting state of Na${}_x$CoO${}_2\cdot y$H${}_2$O
• Spin correlations and cobalt charge states: A new phase diagram of sodium cobaltates
• Triangular Spin-Orbit-Coupled Lattice with Strong Coulomb Correlations: Sn Atoms on a SiC(0001) Substrate
• Nonlinear current-voltage behavior and electrically driven phase transition in charge frustrated LuFe2O4
• ^{59}Co NMR evidence for charge ordering below T_{CO}\sim 51 K in Na_{0.5}CoO_2
• Extended Gutzwiller Approximation for Inhomogeneous System
• Itinerant and localized magnetism on the triangular lattice: sodium rich phases of Na${}_x$CoO${}_2$
• Rearrangement of Sodium ordering and its effect on physical properties in $N{a}_{x}Co{O}_2$ system
• Emergent charge ordering in near half doped Na${}_{0.46}$CoO${}_2$
• Interplay of magnetism and superconductivity in 2D extended Hubbard model
• NMR studies of Successive Phase Transitions in Na0.5CoO2 and K0.5CoO2
• Temperature-driven sodium-ion dynamical-to-static crossover in the zig-zag ordered phase of Na${}_{0.5}$CoO${}_2$