The electronic properties of the heavy metal superconductor [Formula: see text] are reported. The estimated superconducting parameters obtained from physical properties measurements indicate that [Formula: see text] is a BCS-type superconductor. Electronic band structure calculations show that Ir d-states dominate the Fermi level. A comparison of electronic band structures of [Formula: see text] and [Formula: see text] shows that the Ir-compound has a strong spin-orbit-coupling effect, which creates a complex Fermi surface.
We study a doped two-dimensional bosonic Hubbard model with two hard-core species using quantum Monte Carlo simulations. With doping we find five distinct phases, including a normal liquid at higher temperature, an anti-ferromagnetically ordered Mott insulator, a region of coexistent anti-ferromagnetic and superfluid phases near half filling, and further away from half filling, a superfluid phase and a phase separated ferromagnet. In the latter, the heavy species has Mott behavior with integer fillings, while the light species shows Mott and superfluid behaviors. The global entropy of this phase is relatively high which may provide a new avenue to obtain a polarized phase or a Mott insulator in cold atom experiments.
We study the Bose-Hubbard model in the presence of on-site disorder in the canonical ensemble and conclude that the local density of the Bose glass phase behaves differently at incommensurate filling than it does at commensurate one. Scaling of the superfluid density at incommensurate filling of ρ = 1.1 and on-site interaction U = 80t predicts a superfluid-Bose glass transition at disorder strength of ∆c ≈ 30t. At this filling the local density distribution shows skew behavior with increasing disorder strength. Multifractal analysis also suggests a multifractal behavior resembling that of the Anderson localization. Percolation analysis points to a phase transition of percolating non-integer filled sites around the same value of disorder. Our findings support the scenario of percolating superfluid clusters enhancing Anderson localization near the superfluid-Bose glass transition. On the other hand, the behavior of the commensurate filled system is rather different. Close to the tip of the Mott lobe (ρ = 1, U = 22t) we find a Mott insulator-Bose glass transition at disorder strength of ∆c ≈ 16t. An analysis of the local density distribution shows Gaussian like behavior for a wide range of disorders above and below the transition. The behaviors of the superfluid-Bose glass transition call for a thorough finite size scaling analysis of percolation and multifractality to understand the universality of the transition.
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