Surface-Plasmon-Assisted Cooper Pair Formation in Ordered Gold Films at Room Temperature

Abstract

Electron emission induced by surface plasmon polaritons (SPPs) or simply surface plasmons excited by high-intensity femtosecond laser irradiation of an ordered Au surface has been studied by time-of-flight (TOF) analysis of the emitted electrons. Significant differences have been found compared to the same analysis of smooth surfaces. The SPP field enhancement has been significantly increased in hot spots which have the same periodicity as the surface. In addition to the increased field enhancement, periodic narrow peaks have been detected in the TOF spectrum. In the laser intensity range, where the high-energy peak is present, some of (also periodic in time) less frequent narrow peaks are about twice as large as the remaining ones, indicating the detection of two electrons (Cooper pairs) at about the same time, namely within the resolution of the TOF spectrometer.