Suchergebnisse

We analyze the microscopic origin and the physical properties of the superconducting phase recently observed in MoS2. We show how the combination of the valley structure of the conduction band, the density dependence of the screening of the long-range Coulomb interactions, the short-range electronic repulsion, and the relative weakness of the electron-phonon interactions makes possible the existence of a phase where the superconducting order parameter has opposite signs in different valleys, resembling the superconductivity found in the pnictides and cuprates. © 2013 American Physical Society. ; F.G. acknowledges financial support fromMINECO, Spain, through Grant No. FIS2011-23713, and the European Union, through Grant No. 290846. R.R. acknowledges financial support from the Juan de la Cierva Program (MINECO, Spain). E.C. acknowledges the Marie CurieGrant No. PIEF-GA-2009-251904. ; Peer Reviewed

In this paper we present a paradigmatic tight-binding model for single-layer as well as multilayered semiconducting MoS2 and similar transition metal dichalcogenides. We show that the electronic properties of multilayer systems can be reproduced in terms of a tight-binding modeling of the single-layer hopping terms by simply adding the proper interlayer hoppings ruled by the chalcogenide atoms. We show that such a tight-binding model makes it possible to understand and control in a natural way the transition between a direct-gap band structure, in single-layer systems, and an indirect gap in multilayer compounds in terms of a momentum/orbital selective interlayer splitting of the relevant valence and conduction bands. The model represents also a suitable playground to investigate in an analytical way strain and finite-size effects. © 2013 American Physical Society. ; F.G. acknowledges financial support from MINECO, Spain, through Grant No. FIS2011-23713, and the European Union, through Grant No. 290846. R.R. acknowledges financial support from the Juan de la Cierva Program (MINECO, Spain). E.C. acknowledge support from the European FP7 Marie Curie Project No. PIEF-GA-2009-251904. J.A.S.-G. and P.O. acknowledge support from Spanish MINECO (Grants No. FIS2009-12721-C04-01, No. FIS2012-37549-C05-02, and No. CSD2007-00050). J.A.S.-G. was supported by an FPI Fellowship from MINECO. ; Peer Reviewed

The electrostatic screening in single and few-layer MoS2 sheets is studied. Electrostatic force microscopy is used to probe the electric field generated by charge impurities in the substrate and incompletely screened by MoS2 sheets. A non-linear Thomas-Fermi theory is employed to interpret the experimental results, demonstrating the important role of the interlayer coupling in the screening of MoS2. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. ; This work was supported by MICINN/MINECO (Spain) through the programs MAT2011-25046 and CONSOLIDER-INGENIO-2010 "Nanociencia Molecular" CSD-2007-00010, Comunidad de Madrid through program Nanobiomagnet S2009/MAT-1726 and the European Union (FP7) through the programs RODIN and ELFOS. E.C. acknowledges a Marie Curie Grant, PIEF-GA-2009-251904. ; Peer Reviewed

Controlling the bandstructure through local-strain engineering is an exciting avenue for tailoring optoelectronic properties of materials at the nanoscale. Atomically thin materials are particularly well-suited for this purpose because they can withstand extreme nonhomogeneous deformations before rupture. Here, we study the effect of large localized strain in the electronic bandstructure of atomically thin MoS2. Using photoluminescence imaging, we observe a strain-induced reduction of the direct bandgap and funneling of photogenerated excitons toward regions of higher strain. To understand these results, we develop a nonuniform tight-binding model to calculate the electronic properties of MoS2 nanolayers with complex and realistic local strain geometries, finding good agreement with our experimental results. © 2013 American Chemical Society. ; This work was supported by the European Union (FP7) through the program RODIN and the Dutch organization for Fundamental Research on Matter (FOM). A.C.-G. acknowledges financial support through the FP7-Marie Curie Project PIEF-GA-2011- 300802 ("STRENGTHNANO"). R.R. acknowledges financial support from the Juan de la Cierva Program (MINECO, Spain). E.C. acknowledges financial support through the FP7-Marie Curie Project PIEF-GA-2009-251904. F.G. and R.R. acknowledge support from MINECO (Spain), through grant FIS2011-23713 and ERC Advanced grant no. 290846. ; Peer Reviewed