Long-range repulsive interaction between TTF molecules on a metal surface induced by charge transfer

The low-coverage adsorption of a molecular electron donor, tetrathiafulvalene, on Au(111) is characterized by the spontaneous formation of superlattice of monomers, whose spacing exceeds the equilibrium distance of non-covalent interactions and depends on coverage. The origin of this peculiar growth mode is due to a long-range repulsive interaction between molecules. The analysis of molecular-pair distributions obtained by scanning tunneling microscopy measurements permits us to determine that the nature of TTF intermolecular interactions on Au (111) is electrostatic. A repulsion between molecules is caused by the accumulation of charge due to electron donation into the metal surface, as pictured through density functional theory calculations

Recombination limited energy relaxation in a BCS superconductor

We study quasiparticle energy relaxation at sub-kelvin temperatures by injecting hot electrons into an aluminium island and measuring the energy flux from electrons into phonons both in the superconducting and in the normal state. The data show strong reduction of the flux at low temperatures in the superconducting state, in qualitative agreement with the presented quasiclassical theory for clean superconductors. Quantitatively, the energy flux exceeds that from the theory both in the superconducting and in the normal state, possibly suggesting an enhanced or additional relaxation process

TELEPENSOUTH project: Measurement of the Earth gravitomagnetic field in a terrestrial laboratory

We will expose a preliminary study on the feasibility of an experiment leading to a direct measurement of the gravitomagnetic field generated by the rotational motion of the Earth. This measurement would be achieved by means of an appropriate coupling of a TELEscope and a Foucault PENdulum in a laboratory on ground, preferably at the SOUTH pole. An experiment of this kind was firstly proposed by Braginski, Polnarev and Thorne, 18 years ago, but it was never re-analyzed.Comment: 7 pages, LaTeX, Springer style files included. Contribution to the Proceedings of the Spanish Relativity Meeting-ERE-2001 (Madrid, September 2001). To appear in the book "Relativistic Astrophysics", Lecture Notes in Physics, Springer Verlag (2002), edited by L. Fernandez-Jambrina, L.M. Gonzalez-Romer

Tunable crystal structure and proton conductivity of lanthanide nitrilotrismethylphosphonates

Metal phosphonates are multifunctional solids with remarkable stability and proton conducting properties owing to their structure is usually composed of extended hydrogen-bond networks that favor proton transfer pathways [1]. Moreover, these properties can be enhanced by appropriate modification of the synthesis conditions [2, 3]. In this communication, a new family of isostructural 2D layered compounds based on lanthanide nitrilotris-methylphosphonates is reported. These compounds have been isolated at room temperature and have the general formula Ln[N(CH2)3(PO3H2)2(PO3H)(H2O)]SO4·2H2O (Ln= Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er and Yb). The coordination environment of Ln3+ is composed by eight oxygen atoms from three different ligands and two oxygens from bound waters. This connectivity creates positive charged layers connected to sulfate ions through hydrogen-bonds. These compounds show promising proton conductivity with values ranging between 7.6·10-2 and 3.8·10-2 S·cm-1 at 80 °C and 95% RH and low activation energy corresponding to Grotthuss-type proton transfer mechanism. In addition, a structural transformation occurs at T > 70 °C accompanied by a remarkable enhanced conductivity. Studies on the structure-properties relationships will be discussed.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. MINECO: MAT2016-77648-R Junta Andalucía: P12-FQM-1656 y FQM-11