An Electronic Model for CoO2 layer based systems: Chiral RVB metal and Superconductivity
نویسنده
چکیده
Takada et al. have reported superconductivity in layered NaxCoO2.yH2O (Tc ≈ 5 K) and more recently Wen et al. in AxCoO2+δ (A = Na, K)(Tc ≈ 31 K). We model a reference neutral CoO2 layer as an orbitally non-degenerate spin1 2 antiferromagnetic Mott insulator on a triangular lattice and NaxCoO2.yH2O and AxCoO2+δ as electron doped Mott insulators described by a tJ model. It is suggested that at optimal doping chiral spin fluctuations enhanced by the dopant dynamics leads to a d-wave superconducting state. A chiral RVB metal, a PT violating state with condensed RVB gauge fields, with a possible weak ferromagnetism and low temperature p-wave superconductivity are also suggested at higher dopings.
منابع مشابه
Structure and Dynamics of NaxCoO2 and the Hydrated Superconductor
The properties of the NaxCoO2 class of materials are of interest from a number of viewpoints. These compounds are based on a triangular lattice of spin-1⁄2 ions—prototype RVB system— where a high thermoelectric-power Curie-Weiss metallic paramagnet is found for Na0.7CoO2, a charge ordered insulator at x=0.5, and a paramagnetic metal where superconductivity is induced in Na0.3CoO2 when it is int...
متن کاملRVB Contribution to Superconductivity in MgB2
We view MgB2 as electronically equivalent to (non-staggered) graphite (B − layer) that has undergone a zero gap semiconductor to a superconductor phase transition by a large c-axis (chemical) pressure due to Mg layers. Further, like the pπ bonded planar organic molecules, graphite is an old resonating valence bond (RVB) system. The RVB’s are the ‘preexisting cooper pairs’ in the ‘parental’ zero...
متن کاملA new series of sodium cobalt oxyhydrates.
We report a new series of sodium cobalt oxyhydrates that contains the same two dimensional building blocks as superconducting NaxCoO2.yH2O. The absence of superconductivity emphasises the importance of the CoO2 stacking arrangement on the resultant electronic properties.
متن کاملResonating valence bonds and mean-field d-wave superconductivity in graphite
We investigate the possibility of inducing superconductivity in a graphite layer by electronic correlation effects. We use a phenomenological microscopic Hamiltonian which includes nearest neighbor hopping and an interaction term which explicitly favors nearest neighbor spin-singlets through the well-known resonance valence bond (RVB) character of planar organic molecules. Treating this Hamilto...
متن کاملResonating Valence Bond Mechanism of Impurity Band Superconductivity in Diamond
Superconductivity in an uncompensated boron doped diamond, a very recent observation, is strikingly close to an earlier observation of Anderson-Mott insulator to metal transition, prompting us to suggest an electron correlation driven superconductivity in an impurity band. Random coulomb potential remove a three fold orbital degeneracy of boron acceptor states, resulting in an effective single,...
متن کامل