3,024 research outputs found

    Phonon-Mediated High-Temperature Superconductivity in Few-Hydrogen Metal-Bonded Perovskite Al4H\rm {Al_4H} up to 54 K under Ambient Pressure

    Full text link
    Multi-hydrogen lanthanum hydrides have shown the highest critical temperature TcT_c at 250-260 K under 170-200 GPa. However, such high pressure is a great challenge for sample preparation and practical application. To address this challenge, we propose a novel design strategy for high-TcT_c superconductors by constructing new few-hydrogen metal-bonded perovskite hydrides at ambient pressure, such as Al4H\rm {Al_4H}, with better ductility than the well-known multi-hydrogen, cuprate and iron-based superconductors. Based on the Migdal-Eliashberg theory, we predict that the structurally stable Al4H\rm {Al_4H} has a favorable high TcT_c up to 54 K under atmospheric pressure, similar to SmOFeAs.Comment: 6 pages, 4 figure

    Quantum Cloning Machines and the Applications

    Full text link
    No-cloning theorem is fundamental for quantum mechanics and for quantum information science that states an unknown quantum state cannot be cloned perfectly. However, we can try to clone a quantum state approximately with the optimal fidelity, or instead, we can try to clone it perfectly with the largest probability. Thus various quantum cloning machines have been designed for different quantum information protocols. Specifically, quantum cloning machines can be designed to analyze the security of quantum key distribution protocols such as BB84 protocol, six-state protocol, B92 protocol and their generalizations. Some well-known quantum cloning machines include universal quantum cloning machine, phase-covariant cloning machine, the asymmetric quantum cloning machine and the probabilistic quantum cloning machine etc. In the past years, much progress has been made in studying quantum cloning machines and their applications and implementations, both theoretically and experimentally. In this review, we will give a complete description of those important developments about quantum cloning and some related topics. On the other hand, this review is self-consistent, and in particular, we try to present some detailed formulations so that further study can be taken based on those results.Comment: 98 pages, 12 figures, 400+ references. Physics Reports (published online

    Average Density of States in Disordered Graphene systems

    Full text link
    In this paper, the average density of states (ADOS) with a binary alloy disorder in disordered graphene systems are calculated based on the recursion method. We observe an obvious resonant peak caused by interactions with surrounding impurities and an anti-resonance dip in ADOS curves near the Dirac point. We also find that the resonance energy (Er) and the dip position are sensitive to the concentration of disorders (x) and their on-site potentials (v). An linear relation, not only holds when the impurity concentration is low but this relation can be further extended to high impurity concentration regime with certain constraints. We also calculate the ADOS with a finite density of vacancies and compare our results with the previous theoretical results.Comment: 10 pages, 8 figure

    Diaqua­bis­(5-carb­oxy-2-propyl-1H-imidazole-4-carboxyl­ato-κ2 N 3,O 4)cadmium(II) 3.5-hydrate

    Get PDF
    In the title complex, [Cd(C8H9N2O4)2(H2O)2]·3.5H2O, the CdII is coordinated by two water mol­ecules and N,O-chelated by two 5-carb­oxy-2-propyl-1H-imidazole-4-carboxyl­ate anions in a distorted octa­hedral geometry. The two imidazole rings are oriented to each other with a dihedral angle of 75.1 (2)°. Strong O—H⋯O hydrogen bonds between protonated and deprotonated carboxyl­ate groups occur in the mol­ecular structure. In the crystal structure extensive O—H⋯O and N—H⋯O hydrogen bonds help to stabilize the three-dimensional supra­molecular framework. The propyl groups of anions are disordered over two sites with refined occupancies of 0.768 (6):0.232 (6) and 0.642 (8):0.358 (8)
    • …
    corecore