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O: Fachverband Oberflächenphysik

O 82: Metal Substrates II

O 82.2: Vortrag

Donnerstag, 3. April 2014, 16:15–16:30, WIL A317

Reinvestigation of the Acoustic Surface Plasmon Dispersion on Cu(111) by HREELS — •Jan Pischel, Emanuel Welsch, Olaf Skibbe, and Annemarie Pucci — Kirchhoff-Institut für Physik, Im Neuenheimer Feld 227, D-69120 Heidelberg

During the past decade, the existence of the acoustic surface plasmon (ASP, [1]) on various single crystal metal surfaces has been established experimentally, see e. g. [2]. Its low energy in the meV range and a linear dispersion near Γ make it interesting for a wide range of phenomena and applications reaching from superconductivity to nano-optics. Only recently, it was reported that the ASP on Au(111) disperses into the electron-hole (e-h) pair continuum [3], which is in contrast to the theoretical prediction [1]. This unexpected behaviour could be traced back to the fact that the majority of bulk electrons around the Fermi level move slower than the electrons of the Shockley surface state and are hence screened by the latter rather than the other way around.

We used HREELS with low impact energies down to 2eV and an angular resolution of 1.4^∘ to reinvestigate the situation on Cu(111). As shown here, the ASP turned out to be only one of multiple contributions to the broad excitation feature that was earlier exclusively ascribed to the ASP [2] and to disperse into the e-h pair continuum. These results suggest that a situation similar to the Au(111) case must be present on the Cu(111) surface, too.

[1] Silkin et al., Europhys. Lett. 66(2):260–264, 2004.

[2] Pohl et al., Europhys. Lett. 90:57006, 2010.

[3] Vattuone et al., Phys. Rev. Lett. 110:127405, 2013.