Quasiperiodic free electron metal layers

A. K. Shukla, R. S. Dhaka, S. W. D’Souza, Sanjay Singh, D. Wu, T. A. Lograsso, M. Krajč́ı, J. Hafner, K. Horn, and S. R. Barman UGC-DAE Consortium for Scientific Research, Khandwa Road, Indore, 452001, India. Ames Laboratory U.S. DOE, Iowa State University, Ames, Iowa 50011-3020, USA. Institute of Physics, Slovak Academy of Sciences, SK-84511 Bratislava, Slovak Republic Center for Computational Materials Science, Universität Wien, A-1090 Wien, Austria and Fritz-Haber-Institut der Max-Planck-Gesellschaft, D-14195 Berlin, Germany Abstract Using electron diffraction, we show that free electron metals such as sodium and potassium form a highly regular quasiperiodic monolayer on the fivefold surface of icosahedral Al-Pd-Mn and that the quasiperiodicity propagates up to the second layer in sodium. Our photoelectron spectroscopy results show that the quasicrystalline alkali metal adlayer does not exhibit a pseudogap near the Fermi level, thought to be charactersitic for the electronic structure of quasicrystalline materials. Calculations based on density functional theory provide a model structure for the quasicrystalline alkali metal monolayer and confirm the absence of a pseudogap.