Attosecond control of electrons emitted from a nanoscale metal tip (1107.1591v1)

Abstract: Attosecond science is based on steering of electrons with the electric field of well-controlled femtosecond laser pulses. It has led to, for example, the generation of XUV light pulses with a duration in the sub-100-attosecond regime, to the measurement of intra-molecular dynamics by diffraction of an electron taken from the molecule under scrutiny, and to novel ultrafast electron holography. All these effects have been observed with atoms or molecules in the gas phase. Although predicted to occur, a strong light-phase sensitivity of electrons liberated by few-cycle laser pulses from solids has hitherto been elusive. Here we show a carrier-envelope (C-E) phase-dependent current modulation of up to 100% recorded in spectra of electrons laser-emitted from a nanometric tungsten tip. Controlled by the C-E phase, electrons originate from either one or two sub-500as long instances within the 6-fs laser pulse, leading to the presence or absence of spectral interference. We also show that coherent elastic re-scattering of liberated electrons takes place at the metal surface. Due to field enhancement at the tip, a simple laser oscillator suffices to reach the required peak electric field strengths, allowing attosecond science experiments to be performed at the 100-Megahertz repetition rate level and rendering complex amplified laser systems dispensable. Practically, this work represents a simple, exquisitely sensitive C-E phase sensor device, which can be shrunk in volume down to ~ 1cm3. The results indicate that the above-mentioned novel attosecond science techniques developed with and for atoms and molecules can also be employed with solids. In particular, we foresee sub-femtosecond (sub-) nanometre probing of (collective) electron dynamics, such as plasmon polaritons, in solid-state systems ranging in size from mesoscopic solids via clusters to single protruding atoms.

• The paper shows a breakthrough in attosecond control by modulating electron emissions from a tungsten nanotip with up to 100% efficiency.
• The experiments employed few-cycle laser oscillators to generate sub-500 attosecond electron bursts via precise C-E phase control.
• The findings expand attosecond techniques to solid-state systems, paving the way for ultrafast electronic devices operating at optical frequencies.

Attosecond Control of Electrons Emitted from a Nanoscale Metal Tip

The paper "Attosecond control of electrons emitted from a nanoscale metal tip" by Krüger, Schenk, and Hommelhoff presents a detailed investigation into the control of electron emissions utilizing attosecond science. The paper achieves notable progress in understanding and manipulating electron dynamics via the carrier-envelope (C-E) phase, a crucial advancement for attosecond science applications.

Summary of Findings

The authors successfully demonstrate a C-E phase-dependent modulation of electron currents emitted from a tungsten tip, evidencing up to 100% modulation in electron spectra. This substantial modulation underscores the ability to manipulate electron emission with precise attosecond timing. Notably, electron emissions are dictated by sub-500 attosecond instants within the 6-femtosecond laser pulses, resulting in distinct interference patterns that are indicative of coherent re-scattering processes at the metal surface.

The experiments were executed using a few-cycle laser oscillator focused on a metal nanotip, achieving field enhancement and allowing attosecond science experiments to be performed without complex amplified laser systems. This approach not only simplifies setups but also suggests potential for low-energy, high-repetition-rate attosecond applications using compact, sensitive C-E phase sensors.

Implications

The implications of these findings are broad, both for fundamental science and potential applications. By affirming the capability to harness attosecond techniques with solids, the research expands the domain of attosecond physics beyond atoms and molecules, encompassing solid-state systems. The prospect of sub-femtosecond probing of electron dynamics opens new vistas for examining effects such as plasmon polaritons in nanoscale materials. This aligns with the ongoing interest in advancing ultrafast electron holography and electron emission mechanisms at nanostructures.

Practically, the use of a nanoscale tip as an electron emitter suggests potential for developing extremely fast electronic devices, conceptually akin to optical attosecond field-effect transistors. The findings pave the way for real-world applications in electronics, potentially allowing operations at optical frequencies, thus marking a significant stride towards the realization of lightwave electronics.

Theoretical and Experimental Corroboration

The experiment’s outcomes are well-supported by theoretical models. The semiclassical Simple Man’s Model (SMM) and a quantum mechanical approach via the time-dependent Schrödinger equation (TDSE) both offer qualitative predictions aligning with the observed phenomena. The analysis confirms that C-E phase effects play a pivotal role in the spectral structure and kinetic energy distribution of emitted electrons.

Future Directions

The results hint at vast potential for further research. Extensions could include investigations into different materials with strong plasmonic behavior, such as silver, offering insights into collective electron dynamics. Additionally, enhancing the models to integrate multi-state dynamics could further elucidate the processes underpinning attosecond photoemissions, especially considering plasmonic effects.

Conclusion

This work significantly contributes to our comprehension of electron dynamics on sub-femtosecond timescales from solid surfaces. The approach of using a few-cycle laser in conjunction with a nanoscale metal tip exemplifies the innovative manipulation of electron emissions, broadening the technological horizons for ultrafast electronic devices and attosecond research methodologies. Thus, it lays the groundwork for an evolution from the traditional paradigms of electron emission and manipulation, potentially bridging the gap between current electronic devices and future lightwave-based systems.