Surface-plasmon-assisted electron pair formation in strong electromagnetic field

Kroó, Norbert and Rácz, Péter and Varró, Sándor (2014) Surface-plasmon-assisted electron pair formation in strong electromagnetic field. EUROPHYSICS LETTERS, 105 (6). ISSN 0295-5075

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Abstract

The basis of low-temperature superconductivity has been set to be the pair formation of electrons, due to their effective attraction. The appearance of an effective attraction potential has also been predicted for electron-electron scattering in the presence of strong, inhomogeneous radiation field. In the present work the strong electromagnetic fields were created by femtosecond Ti:Sa lasers, used to excite surface plasmons in gold films at room temperature in the Kretschmann geometry. Experimental investigations were carried out using a surface plasmon near field scanning tunneling microscope, measuring it’s response to the excitation at hot spots on the gold surface. Furthermore, the spectra of photoelectrons, liberated by multi-plasmon absorption, has also been measured by a time- of-flight spectrometer. In both cases new type of anomalies in the electron signal have been measured in the same intensity range, whose existence may be qualitatively understood, by using the intensity-dependent expression for the effective electron- electron scattering potential, derived earlier in a different context.

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