Vortex State in Na_xCoO_2.yH_2O: p_x\pm ip_y-wave versus d_{x^2-y^2}\pm id_{xy}-wave Pairing

Abstract

Based on an effective Hamiltonian specified in the triangular lattice with possible $p_x\pm i{p}_y$- or $d_{x^2-y^2}\pm i{d}_{xy}$-wave pairing, which has close relevance to the newly discovered Na${}_{0.35}$CoO${}_2$$\cdot y$H${}_2$O, the electronic structure of the vortex state is studied by solving the Bogoliubov-de Gennes equations. It is found that $p_x\pm i{p}_y$-wave is favored for the electron doping as the hopping integral $t<0$. The lowest-lying vortex bound states are found to have respectively zero and positive energies for $p_x\pm i{p}_y$- and $d_{x^2-y^2}\pm i{d}_{xy}$-wave superconductors, whose vortex structures exhibit the intriguing six-fold symmetry. In the presence of strong on-site repulsion, the antiferromagnetic and ferromagnetic orders are induced around the vortex cores for the former and the latter, respectively, both of which cause the splitting of the LDOS peaks due to the lifting of spin degeneracy. STM and NMR measurements are able to probe the new features of vortex states uncovered in this work.

arXiv comment4 pages, 4 figures, The slightly shorter version was submitted to PRL

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• Impurity- and Magnetic-field-induced Quasiparticle States in Chiral $p$-wave Superconductors
• Inducing topological flat bands in bilayer graphene with electric and magnetic superlattices
• Identifying the pairing symmetry in sodium cobalt oxide by Andreev edge states
• Nuclear Spin Relaxation Rate of Disordered $p_x+i{p}_y$-wave Superconductors
• Absence of spin susceptibility decrease in a bulk organic superconductor with triangular lattice