Transient excitons at metal surfaces

Cui, Xuefeng; Argondizzo, Adam; Garrett-Roe, Sean; Gumhalter, B.; Petek, Hrvoje

doi:10.1038/nphys2981

Cited by 125 publications

(127 citation statements)

References 35 publications

(11 reference statements)

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“…To get more insight into the electron dynamics that produce the thermionic emission, we measure time-domain interferograms of mPP [38]. Changing the delay τ between identical collinear pump and probe pulses in 50-as steps while recording EðkÞ distributions of mPP records interferometric movies of the nonlinear TES excitation.…”

Section: Resultsmentioning

confidence: 99%

“…At each time delay increment of about 50 as, an EðkÞ distribution is acquired as described elsewhere [38]. To measure delay-dependent hot electron temperatures, the pump-probe delay is fixed to specific values corresponding to integral numbers of optical cycles, and EðkÞ photoelectron distributions are acquired for the double pulse excitation.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…TR-mPP measurements [38,78] are performed on a highly oriented pyrolytic graphite (HOPG). The sample surface is cleaved in air and degassed at 900 K for 10 hours in the ultrahigh vacuum chamber (base pressure <1 × 10 −10 mbar) for photoemission measurements.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…Another feature owing to the 2D character of graphene and graphite is that Coulomb interaction with small momentum transfers is unscreened [25,35,36]. When photoexcitation and subsequent carrier multiplication suddenly raise the free carrier density above the unperturbed value, a new regime of screening with three-dimensional (3D) character can come about in graphite on a time scale of the inverse frequency of the photoexcited plasma [37,38].…”

Section: Introductionmentioning

confidence: 99%

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Ultrafast Multiphoton Thermionic Photoemission from Graphite

et al. 2017

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Electronic heating of cold crystal lattices in nonlinear multiphoton excitation can transiently alter their physical and chemical properties. In metals where free electron densities are high and the relative fraction of photoexcited hot electrons is low, the effects are small, but in semimetals, where the free electron densities are low and the photoexcited densities can overwhelm them, the intense femtosecond laser excitation can induce profound changes. In semimetal graphite and its derivatives, strong optical absorption, weak screening of the Coulomb potential, and high cohesive energy enable extreme hot electron generation and thermalization to be realized under femtosecond laser excitation. We investigate the nonlinear interactions within a hot electron gas in graphite through multiphoton-induced thermionic emission. Unlike the conventional photoelectric effect, within about 25 fs, the memory of the excitation process, where resonant dipole transitions absorb up to eight quanta of light, is erased to produce statistical Boltzmann electron distributions with temperatures exceeding 5000 K; this ultrafast electronic heating causes thermionic emission to occur from the interlayer band of graphite. The nearly instantaneous thermalization of the photoexcited carriers through Coulomb scattering to extreme electronic temperatures characterized by separate electron and hole chemical potentials can enhance hot electron surface femtochemistry, photovoltaic energy conversion, and incandescence, and drive graphite-to-diamond electronic phase transition.

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Section: Resultsmentioning

confidence: 99%

Section: Experimental Methodsmentioning

confidence: 99%

Section: Experimental Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Ultrafast Multiphoton Thermionic Photoemission from Graphite

et al. 2017

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“…In fact, they have attained the role of a kind of drosophila of electron dynamics. As such, they serve as a benchmark system for the development of new ultrafast experimental techniques and as a reference for investigations of more complex electron transfer processes [6][7][8][9][10][11][12][13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Resolubility of image-potential resonances

Höfer

Echenique

2016

Surface Science

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A theory of image-potential states is presented for the general case where these surface electronic states are resonant with a bulk continuum. The theory extends the multiple scattering approach of Echenique and Pendry into the strong coupling regime while retaining independence from specific forms of surface and bulk potentials. The theory predicts the existence of a well-resolved series of resonances for arbitrary coupling strengths. Surprisingly, distinct image-potential resonances are thus expected to exist on almost any metal surface, even in the limiting case of jellium.

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Right On Time: Ultrafast Charge Separation Before Hybrid Exciton Formation

Gierster,

Turkina,

Deinert

et al. 2024

Advanced Science

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Organic/inorganic hybrid systems offer great potential for novel solar cell design combining the tunability of organic chromophore absorption properties with high charge carrier mobilities of inorganic semiconductors. However, often such material combinations do not show the expected performance: while ZnO, for example, basically exhibits all necessary properties for a successful application in light‐harvesting, it was clearly outpaced by TiO2 in terms of charge separation efficiency. The origin of this deficiency has long been debated. This study employs femtosecond time‐resolved photoelectron spectroscopy and many‐body ab initio calculations to identify and quantify all elementary steps leading to the suppression of charge separation at an exemplary organic/ZnO interface. It is demonstrated that charge separation indeed occurs efficiently on ultrafast (350 fs) timescales, but that electrons are recaptured at the interface on a 100 ps timescale and subsequently trapped in a strongly bound (0.7 eV) hybrid exciton state with a lifetime exceeding 5 µs. Thus, initially successful charge separation is followed by delayed electron capture at the interface, leading to apparently low charge separation efficiencies. This finding provides a sufficiently large time frame for counter‐measures in device design to successfully implement specifically ZnO and, moreover, invites material scientists to revisit charge separation in various kinds of previously discarded hybrid systems.

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Transient excitons at metal surfaces

Cited by 125 publications

References 35 publications

Ultrafast Multiphoton Thermionic Photoemission from Graphite

Ultrafast Multiphoton Thermionic Photoemission from Graphite

Resolubility of image-potential resonances

Right On Time: Ultrafast Charge Separation Before Hybrid Exciton Formation

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