Na4Ir3O8 as a 3D Spin Liquid with Fermionic Spinons

Spin liquid states for the spin-12 antiferromagnetic Heisenberg model on a hyperkagome lattice are studied. We classify and study flux states according to symmetries. Applying this model to Na(4)Ir(3)O(8), we propose that the high temperature state may be described by a spinon Fermi surface, which forms a paired state with line nodes below 20 K. The possible mixed spin singlet and spin triplet pairing states are discussed according to the lattice symmetry which breaks inversion.