Lightwave-driven scanning tunnelling spectroscopy of atomically precise graphene nanoribbons

Ammerman, S. E.; Jelic, Vedran; Wei, Y.; Breslin, V. N.; Hassan, Mohamed; Everett, Nathan; Lee, S.; Sun, Qiang; Pignedoli, Carlo A.; Ruffieux, Pascal; Fasel, Román; Cocker, Tyler L.

doi:10.1038/s41467-021-26656-3

Cited by 36 publications

(26 citation statements)

References 56 publications

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“…Five groups of special CEP values were designed and fabricated for special applications. [8][9][10][11][12][13][14][15][16][17] Figure 4a shows the simulation results of transmitted far-field THz temporal waveforms with cross-polarization after subunit A in different arrays. Obviously, when the incident pulse is modulated by different arrays in turn, the CEP shift is clearly observed.…”

Section: Resultsmentioning

confidence: 99%

“…sub-picosecond THz pulse to the nanotip to modulate the bias of the tunnel junction, has achieved atomic resolution on ultrafast timescales. [8][9][10][11][12][13][14][15][16][17] In order to further manipulate light-field-driven processes in the ultrafast and ultrasmall regime, researchers use the CEP of broadband THz pulse to modulate the potential barrier between the nanotip and sample. [10,12,15,17] This strong nonlinear effect is helpful to realize the ultrafast coherent control of electron transport on the atomic scale.…”

mentioning

confidence: 99%

“…[8][9][10][11][12][13][14][15][16][17] In order to further manipulate light-field-driven processes in the ultrafast and ultrasmall regime, researchers use the CEP of broadband THz pulse to modulate the potential barrier between the nanotip and sample. [10,12,15,17] This strong nonlinear effect is helpful to realize the ultrafast coherent control of electron transport on the atomic scale. [18][19][20] Especially, it is vital to switch the polarity of bias at the STM junction by controlling the CEP of the THz pulse.…”

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confidence: 99%

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Flexible THz Carrier‐Envelope Phase Shifter Based on Metamaterials

Quan

Fang

et al. 2022

Advanced Optical Materials

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The ability to manipulate terahertz (THz) waveform is important for its applications. Despite rapid progress in metamaterials (MMs), the carrier‐envelope phase (CEP) control for THz pulse is still challenging due to its broadband feature. THz scanning tunneling microscope (THz‐STM), as an emerging technique combining both high temporal and spatial resolution, imposes additional requirements. Here, an ultra‐thin and flexible THz CEP shifter with five groups of different MM arrays is proposed. The CEP shifter is based on a specified split‐ring resonator with a pair of cross‐oriented gratings to enhance transmission efficiency. Simulation and experimental results show that the CEP of the THz pulse is modulated by passing through different MM arrays in turn, which can be shifted as high as 2π. The CEP shifter has good tolerance to wide‐angle oblique incidence and structural bending, which is expected to be used as a key component for THz‐STM. The structure of the CEP shifter has many potential applications, including THz wave focusing, beam‐steering, spatial phase modulation, and structured light generation.

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Flexible THz Carrier‐Envelope Phase Shifter Based on Metamaterials

Quan

Fang

et al. 2022

Advanced Optical Materials

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“…The terahertz (THz) region (typically defined between 0.1 THz and 10 THz) has proven to be critical for numerous applications in both fundamental science and industry, including communications [1][2][3], sensing [4], non-invasive imaging [5], nanoscopy [4,6,7] and ultrafast classical and quantum systems. In particular, detecting THz radiation is central to spectroscopy since the THz range hosts low-energy material resonances.…”

Section: Introductionmentioning

confidence: 99%

Terahertz waveform synthesis from integrated lithium niobate circuits

Herter¹,

Shams-Ansari²,

Settembrini³

et al. 2022

Preprint

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Bridging the "terahertz (THz) gap" relies upon synthesizing arbitrary waveforms in the THz domain enabling applications that require both narrow band sources for sensing and few-cycle drives for classical and quantum objects. However, realization of custom-tailored waveforms needed for these applications is currently hindered due to limited flexibility for optical rectification of femtosecond pulses in bulk crystals. Here, we experimentally demonstrate that thin-film lithium niobate (TFLN) circuits provide a versatile solution for such waveform synthesis through combining the merits of complex integrated architectures, low-loss distribution of pump pulses on-chip, and an efficient optical rectification. Our distributed pulse phase-matching scheme grants shaping the temporal, spectral, phase, amplitude, and farfield characteristics of the emitted THz field through designer on-chip components. This strictly circumvents prior limitations caused by the phase-delay mismatch in conventional systems and relaxes the requirement for cumbersome spectral pre-engineering of the pumping light. We provide a toolbox of basic blocks that produce broadband emission up to 680 GHz with adaptable phase and coherence properties by using near-infrared pump pulse energies below 100 pJ.

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“… 6 − 8 In contrast, lightwave-driven STM operates in the strong-field regime, where an intense localized light field of several V/nm modulates the junction barrier and, hence, the tunneling current on subcycle time scales. 2 , 4 , 5 , 9 − 13 The two regimes are commonly distinguished by the Keldysh parameter, , relating the work function of the material, , to the photon energy, , and the light field, . 14…”

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confidence: 99%

Femtosecond Thermal and Nonthermal Hot Electron Tunneling Inside a Photoexcited Tunnel Junction

et al. 2022

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Efficient operation of electronic nanodevices at ultrafast speeds requires understanding and control of the currents generated by femtosecond bursts of light. Ultrafast laser-induced currents in metallic nanojunctions can originate from photoassisted hot electron tunneling or lightwave-induced tunneling. Both processes can drive localized photocurrents inside a scanning tunneling microscope (STM) on femto- to attosecond time scales, enabling ultrafast STM with atomic spatial resolution. Femtosecond laser excitation of a metallic nanojunction, however, also leads to the formation of a transient thermalized electron distribution, but the tunneling of thermalized hot electrons on time scales faster than electron–lattice equilibration is not well understood. Here, we investigate ultrafast electronic heating and transient thermionic tunneling inside a metallic photoexcited tunnel junction and its role in the generation of ultrafast photocurrents in STM. Phase-resolved sampling of broadband terahertz (THz) pulses via the THz-field-induced modulation of ultrafast photocurrents allows us to probe the electronic temperature evolution inside the STM tip and to observe the competition between instantaneous and delayed tunneling due to nonthermal and thermal hot electron distributions in real time. Our results reveal the pronounced nonthermal character of photoinduced hot electron tunneling and provide a detailed microscopic understanding of hot electron dynamics inside a laser-excited tunnel junction.

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Lightwave-driven scanning tunnelling spectroscopy of atomically precise graphene nanoribbons

Cited by 36 publications

References 56 publications

Flexible THz Carrier‐Envelope Phase Shifter Based on Metamaterials

Flexible THz Carrier‐Envelope Phase Shifter Based on Metamaterials

Terahertz waveform synthesis from integrated lithium niobate circuits

Femtosecond Thermal and Nonthermal Hot Electron Tunneling Inside a Photoexcited Tunnel Junction

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