We show that a planar structure, consisting of an ultrathin semiconducting layer topped with a solid nanoscopically perforated metallic film and then a dielectric interference film, can highly absorb (superabsorb) electromagnetic radiation in the entire visible range, and thus can become a platform for high-efficiency solar cells. The perforated metallic film and the ultrathin absorber in this broadband superabsorber form a metamaterial effective film, which negatively refracts light in this broad frequency range. Our quantitative simulations confirm that the superabsorption bandwidth is maximized at the checkerboard pattern of the perforations. These simulations show also that the energy conversion efficiency of a single-junction amorphous silicon solar cell based on our optimized structure can exceed 12%.

The two-dimensional half-filled extended Hubbard model is studied by means of Quantum Monte Carlo simulation. The model includes the on-site electron interaction (U) and nearest-neighbor interaction (V). We study the formation of antiferromagnetic, charge-density-wave, and superconducting states of the model as the parameters of the model are varied.

Majorana zero-energy bound states (ZEBSs) have been proposed to exist at the ends of one-dimensional Rashba nanowires proximity-coupled to an s-wave superconductor in an external magnetic field induced Zeeman field 1,2 . Such hybrid structures have been a central platform in the search for non-Abelian Majorana zero modes (MZMs) toward fault-tolerant topological quantum computing 3,4 . Here we report the discovery of ZEBSs simultaneously appearing at each end of a one-dimensional atomic line defect in monolayer iron-based high-temperature superconductor FeTe 0.5 Se 0.5 films grown on SrTiO 3 (001) substrates. The spectroscopic properties of the ZEBSs, including the temperature and tunneling barrier dependences, as well as their fusion induced by coupling on line defects of different lengths are found to be robust and consistent with those of the MZMs. These observations suggest a realization of topological Shockley defects at the ends of an atomic line defect in a two-dimensional s-wave superconductor that can host a Kramers pair of MZMs protected by time-reversal symmetry along the chain. Our findings reveal an unprecedented class of topological line defect excitations in two-dimensional superconductor FeTe 0.5 Se 0.5 monolayer films and offer an advantageous platform for generating topological zero-energy excitations at higher operating temperatures, in a single material, and under zero external magnetic field.Zero-energy bound states (ZEBSs) localized at defects and ends of superconductors have attracted tremendous interests recently. Such exotic excitations, known as Majorana zero modes (MZMs) that are self-conjugate and obey non-Abelian statistics, have been shown theoretically to exist in the vortex core of certain p+ip topological superconductors 5,6 and at the ends of one-dimensional spinless p-wave topological superconductors 7 . MZMs can be used to construct nonlocal topological qubits which are robust against local perturbations as the basic building block for fault-tolerant topological quantum computing. While the search for intrinsic topological superconductors has been extremely challenging and yet unsuccessful, the recent interests in this direction have surged following the realization that producing the MZMs does not require an intrinsic topological superconductor. Fu and Kane proposed that when superconductivity is induced in the helical Dirac fermion surface states of a three-dimensional strong topological insulator by proximity coupling to an s-wave superconductor, a MZM would arise in the vortex core 8 . In the presence of Rashba spin-orbit coupling (RSOC), MZMs were predicted to arise at the two ends of a nanowire proximity coupled to an s-wave superconductor and a time-reversal symmetry breaking Zeeman field 1,2 .

We generalize the typical medium dynamical cluster approximation to multiband disordered systems. Using our extended formalism, we perform a systematic study of the non-local correlation effects induced by disorder on the density of states and the mobility edge of the three-dimensional two-band Anderson model. We include inter-band and intra-band hopping and an intra-band disorder potential. Our results are consistent with the ones obtained by the transfer matrix and the kernel polynomial methods. We apply the method to KxFe2−ySe2 with Fe vacancies. Despite the strong vacancy disorder and anisotropy, we find the material is not an Anderson insulator. Our results demonstrate the application of the typical medium dynamical cluster approximation method to study Anderson localization in real materials.