Interaction of ultrashort laser pulses with metal nanotips: a model system for strong-field phenomena

Michael Krüger,Georg Wachter,Peter Hommelhoff,Christoph Lemell,Markus Schenk,Joachim Burgdörfer

doi:10.1088/1367-2630/14/8/085019

Michael Krüger, Georg Wachter + Show 4 more

Open Access

https://doi.org/10.1088/1367-2630/14/8/085019

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Abstract

We discuss the interaction of ultrashort near-infrared laser pulses with sharp metal tips at moderate nominal intensities (I0 ∼ 1011 W cm−2). As external electric fields are strongly enhanced at such tips (enhancement factor ∼10) our system turns out to be an ideal miniature laboratory to investigate strong-field effects at solid surfaces. We analyse the electron-energy spectra as a function of the strength of the laser field and the static extraction field and present an intuitive model for their interpretation. The size of the effective field acting on the metal electrons can be determined from the electron spectra. The latter are also reproduced by time-dependent density functional theory (TDDFT) simulations.

Highlights

OAP emitter surface by virtue of field emission microscopy (FEM) [20] and field ion microscopy (FIM) [21], the latter with atomic resolution
Laser–nanotip interactions are ideally suited for exploring the influence of additional static electric fields
We explore both experimentally and theoretically the influence of a superimposed dc field on the formation of the photoelectron spectrum and the plateau, the hallmark of rescattering of a strongly driven electron wavepacket

Summary

F Spectrometer

Emitter surface by virtue of field emission microscopy (FEM) [20] and field ion microscopy (FIM) [21], the latter with atomic resolution. Laser–nanotip interactions are ideally suited for exploring the influence of additional static electric fields. We explore both experimentally and theoretically the influence of a superimposed dc field on the formation of the photoelectron spectrum and the plateau, the hallmark of rescattering of a strongly driven electron wavepacket. For a tungsten tip the experimentally observed electron spectrum can be surprisingly well ‘synthesized’ by a remarkably simple model which can be viewed as the extension of the well-known simple man’s model (SMM) to the nanotip geometry. Despite the apparent complexity of the target, the SMM for nanotips (SMMN) is conceptionally simpler than for atoms or molecules due to the effective reduction of the dynamically relevant degrees of freedom

Experimental methods and results

The simple man’s model for nanotips

Time-dependent density functional theory simulations

Conclusions