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FRG: Quantum Engineering of Metallic and Magnetic Nanostructures

FRG: Quantum Engineering of Metallic and Magnetic Nanostructures Chih-Kang Shih, University of Texas – Austin, DMR 0606485. Tuning the Quantum Stability and Superconductivity of Ultrathin Metal Alloys.

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FRG: Quantum Engineering of Metallic and Magnetic Nanostructures

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  1. FRG: Quantum Engineering of Metallic and Magnetic Nanostructures Chih-Kang Shih, University of Texas – Austin, DMR 0606485 Tuning the Quantum Stability and Superconductivity of Ultrathin Metal Alloys Vertical confinement of valence electrons in ultrathin lead films leads to quantum oscillations in the morphological stability of the film. The stability and superconductive properties of the lead films are tuned via bismuth doping, employing the previously established “electronic growth” concept. Results indicate that the isotropic symmetry of the superconducting Cooper pairs in bulk lead-bismuth alloys is significantly altered in this ultrathin quantum regime. The tunability of the structure and superconductive properties of these novel “quantum metallic alloys” offers exciting possibilities for fundamental studies of superconductivity at the nanoscale. Top: Scanning tunneling microscopy images revealing the quantum growth mode of the Pb-Bi alloy films. Bottom: Oscillations in the quantum stability of a PbBiquantum alloy, calculated with Density Functional Theory. Published in Science316, 1594 (2007).

  2. FRG: Quantum Engineering of Metallic and Magnetic Nanostructures Chih-Kang Shih, University of Texas – Austin, DMR 0606485 Visualizing Bloch Bands and Minigaps in Ultrathin Ag Films 11Å = 3.7 h • Atomically flat, ultra-thin Ag film (2 nm) grown on GaAs exhibit periodic (top figure) as well as quasiperiodic superstructures with unprecedented regularity and clarity. • Local density of states, mapped out by low temperature STM, show interference patterns from coherent scattering of electron waves by the superstructure (bottom left, along periodic direction). • Fourier transform reveals energy-momentum dispersion, showing textbook type Bloch band structure with energy gaps in the periodic direction (bottom right). • Fourier transform along the quasiperiodic direction reveals numerous minigaps in the energy spectrum (not shown). 10 Height (pm) 5 0 0 10 20 30 40 50 Position (Å) 2.0 1.0 E – EF (eV) 1.1 nm 0 -1.55 0 1.55 0 77 y (Å) ky (Å-1) Phys Rev Lett 97, 206102 (2006)

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