Field emission at terahertz frequencies: AC-tunneling and ultrafast carrier dynamics

Herink, Georg; Wimmer, Lara; Ropers, Claus

doi:10.1088/1367-2630/16/12/123005

Cited by 79 publications

(70 citation statements)

References 47 publications

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“…This could be attributed to the combined effect of the averaging over different emission sites and consequently different field strengths as discussed above, and different initial states as well as multiple electron emission. A number of recent studies [38][39][40][41] have focused on the excitations of electrons inside the metal and their influence on photoemission. For the low-repetition rate in our experiment, 38 the short laser pulse duration, 40 and the large tip volume compared to etched tips with the same radius, 41 we do not expect to observe a significant contribution of this effect.…”

Section: Resultsmentioning

confidence: 99%

“…A number of recent studies [38][39][40][41] have focused on the excitations of electrons inside the metal and their influence on photoemission. For the low-repetition rate in our experiment, 38 the short laser pulse duration, 40 and the large tip volume compared to etched tips with the same radius, 41 we do not expect to observe a significant contribution of this effect. The data do not provide clear signatures of thermionic emission; however, we expect future dedicated experimental and theoretical studies to shed some more light on this topic.…”

Section: Resultsmentioning

confidence: 99%

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Attosecond-controlled photoemission from metal nanowire tips in the few-electron regime

et al. 2017

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Extreme nonlinear terahertz electro-optics in diamond for ultrafast pulse switching APL Photonics 2, 036106 (2017) Metal nanotip photoemitters have proven to be versatile in fundamental nanoplasmonics research and applications, including, e.g., the generation of ultrafast electron pulses, the adiabatic focusing of plasmons, and as light-triggered electron sources for microscopy. Here, we report the generation of high energy photoelectrons (up to 160 eV) in photoemission from single-crystalline nanowire tips in few-cycle, 750-nm laser fields at peak intensities of (2-7.3) × 10 12 W/cm 2 . Recording the carrier-envelope phase (CEP)-dependent photoemission from the nanowire tips allows us to identify rescattering contributions and also permits us to determine the high-energy cutoff of the electron spectra as a function of laser intensity. So far these types of experiments from metal nanotips have been limited to an emission regime with less than one electron per pulse. We detect up to 13 e/shot and given the limited detection efficiency, we expect up to a few ten times more electrons being emitted from the nanowire. Within the investigated intensity range, we find linear scaling of cutoff energies. The nonlinear scaling of electron count rates is consistent with tunneling photoemission occurring in the absence of significant charge interaction. The high electron energy gain is attributed to field-induced rescattering in the enhanced nanolocalized fields at the wires apex, where a strong CEP-modulation is indicative of the attosecond control of photoemission. © 2017 Author(s)

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Attosecond-controlled photoemission from metal nanowire tips in the few-electron regime

et al. 2017

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“…The high peak electric fields provided by single-cycle light pulses can be harnessed to manipulate and control charge motion in solid-state systems, resulting in electron emission out of metals and semiconductors [1][2][3][4][5][6] or high harmonics generation in dielectrics 7,8 . These processes are of a non-perturbative character and require precise reproducibility of the electric-field profile [9][10][11][12][13][14] .…”

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confidence: 99%

Sub-cycle optical phase control of nanotunnelling in the single-electron regime

et al. 2016

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The high peak electric fields provided by single-cycle light pulses can be harnessed to manipulate and control charge motion in solid-state systems, resulting in electron emission out of metals and semiconductors [1][2][3][4][5][6] or high harmonics generation in dielectrics 7,8 . These processes are of a non-perturbative character and require precise reproducibility of the electric-field profile 9-14 . Here, we vary the carrier-envelope phase of 6-fs-long near-infrared pulses with pJ-level energy to control electronic transport in a laterally confined nanoantenna with an 8 nm gap. Peak current densities of 50 MA cm -2 are achieved, corresponding to the transfer of individual electrons in a half-cycle period of 2 fs. The observed behaviours are made possible by the strong distortion of the effective tunnelling barrier due to the extreme electric fields that the nanostructure provides and sustains under sub-cycle optical biasing. Operating at room temperature and in a standard atmosphere, the performed experiments demonstrate a robust class of nanoelectronic switches gated by phase-locked optical transients of minute energy content.Present-day high-frequency devices operate in the microwave range, but direct control of electron flow by the electric-field profile of few-cycle optical pulses has recently been demonstrated 12,15 . These experiments were based on strong perturbation of the electronic system in a dielectric material, resulting in a large incoherent background current. Nanoscale confinement of the region biased by the optical transient might avoid a significant influence of nonlinear conductivity in an insulating substrate and result in purely coherent tunnelling currents 16 that may be controlled by the precise shape of the electric field cycles. Our approach to reaching this goal is illustrated in the upper part of Fig. 1a. A single-cycle near-infrared pulse (left) is focused to a nanoscale junction of an electronic circuit (centre) with nonlinear and antisymmetric current-voltage (I-V) characteristics (right). An effective bias then arises when the exciting electric field is cosine-shaped (blue transient and blue dot in the I-V scheme) because its extremum occurs only for one polarity. Consequently, the symmetry of electronic transport is broken, even when integrating over the entire transient, and a net tunnelling current of electrons results through the potential barrier represented by the free-space gap (Fig. 1b,c). Our experiment favours tunnelling over other phenomena such as multiphoton ionization 4 by operating with ultrashort pulses and extreme nanoconfinement of the electric field. No background current exists when the control field is sineshaped (red transient and dot in the I-V characteristics, respectively), because positive and negative polarities now have precisely opposite effects. Consequently, the total current amplitude and direction may be set by varying the carrier-envelope phase (CEP), Δφ CEP , of the pulse. Owing to the single-cycle pulse duration, nanoscale constriction and fi...

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“…2(a). When the emission occurs before the terahertz pulse (<-2 ps), we observe a large spread of kinetic energies, resulting from UV emission combined with THz field emission, a phenomenon observed and investigated in [5]. Conversely, when the emission occurs during the terahertz pulse (-2 to 2 ps), we observe a narrow energy spread with energy gain governed by the THz phase at which emission occurs.…”

Section: Resultsmentioning

confidence: 63%