Electronic Structures of Quasiperiodically Modulated Thin Ag films

When electrons move in crystalline solids, the coherent scattering with the periodic potential enables them to sneak by all ions uninhibited, forming Bloch electrons with their own E vs. k dispersion relationship. This ``Bloch description'' underlies the electronic structures of all crystalline solids. In quasicrystals, however, such a description encounters conceptual difficulties since the Bloch theorem no longer applies. While theoretical investigations showed exotic characteristics such as the Cantor-set energy spectrum early experiments did not reveal such exotic properties. Recent attempt to measure E vs. k relation in a quasicrytal using angle-resolved photoemission revealed free-electron like states. Nevertheless, critical questions remain as how electronic states in a quasiperiodic solid differ from those in a periodic solid. By using low-tempeature scanning tunneling spectroscopy (STS) to probe a quasiperiodically modulated Ag metallic thin film, and by using Fourier analysis, we unravel the influences of individual Fourier components of the scattering potential (periodic vs. quasiperiodic) on the electronic structures.