Berlin 2008 – scientific programme

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O: Fachverband Oberflächenphysik

O 35: Symposium: Atomic Wires at Surfaces II
(Invited Speakers: Erio Tosatti, Serge Lemay, Shuji Hasegawa)

O 35.2: Talk

Tuesday, February 26, 2008, 14:30–14:45, HE 101

One-dimensional low energy plasmons in Au atom chains — •Tadaaki Nagao — World Premier International(WPI) Research Center, International Center for Materials Nanoarchitectonics(MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba 305-0044 JAPAN

Sound-wave-like collective excitation in dense one-dimensional (1D) electron systems confined to Au atom chains on the Si(557) surface is investigated [1]. Electron energy loss spectroscopy using a highly collimated slow electron beam has detected a characteristic low-energy 1D plasmon (wire plasmon) that Tomonaga has mentioned in his theory [2]. This plasmon freely propagates along the Au atom chain and appears as that of 1D free electron gas. However, theoretical analysis adopting a quantum-mechanical scheme beyond the free-electron model indicates a significant dynamic exchange-correlation effect due to strong 1D confinement. By cooling to below 100 K, we detected for the first time a significant change in the plasmon dispersion in the tiny momentum and energy region, which definitely reflects a tiny gap opening due to a metal-to-insulator transition of the atom chains. We also detected similar 1D charge excitations on different silicon surfaces.

\noindent [1] T. Nagao, S. Yaginuma, T. Inaoka, T. Sakurai, Phys. Rev. Lett. 97, 116802 (2006).

\noindent [2] S. Tomonaga, Prog. Theor. Phys. 5, 544(1950).