Loop Current and Orbital Magnetism in Pyrite-Type Ir₃Ch₈ (Ch=Se,Te)

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We study the parent compound of the pyrite-type IrₓCh₂ iridium chalcogenide superconductors, Ir₀.₇₅Ch₂ (or Ir₃Ch₈). While the lattice structure of the material is rather complicated, we show that the electron physics near the Fermi surface (FS) can be described by a three-band tight-binding model. We find that the material possesses a loop current ground state which is responsible for the highly anisotropic strong diamagnetism observed in experiments. The fluctuations of this loop current state can be a possible pairing mechanism for superconductivity.