Attosecond transient reflectivity of electron dynamics in germanium

Kraus, Peter M.; Kaplan, Christopher J.; Borja, Lauren J.; Zürch, Michael; Chang, Hung-Tzu; Jager, Marieke F.; Ott, Christian; Currier, Kayla; Neumark, Daniel M.; Leone, Stephen R.

doi:10.1364/up.2016.uth5a.6

Cited by 2 publications

(2 citation statements)

References 7 publications

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“…Converting the ultrashort pump pulse into the ultraviolet-to-blue spectral region 27 will allow the investigation of wide-bandgap materials. ATAS provides not just the necessary temporal resolution to, in principle, capture sub-cycle carrier dynamics of both carrier species 28 , but also the necessary continuous XUV bandwidth to capture the more than 4 eV wide dynamical features (Fig. 3a) in parallel.…”

Section: Discussionmentioning

confidence: 99%

Direct and simultaneous observation of ultrafast electron and hole dynamics in germanium

et al. 2017

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Understanding excited carrier dynamics in semiconductors is crucial for the development of photovoltaics and efficient photonic devices. However, overlapping spectral features in optical pump-probe spectroscopy often render assignments of separate electron and hole carrier dynamics ambiguous. Here, ultrafast electron and hole dynamics in germanium nanocrystalline thin films are directly and simultaneously observed by ultrafast transient absorption spectroscopy in the extreme ultraviolet at the germanium M4,5 edge. We decompose the spectra into contributions of electronic state blocking and photo-induced band shifts at a carrier density of 8 × 1020 cm−3. Separate electron and hole relaxation times are observed as a function of hot carrier energies. A first-order electron and hole decay of ∼1 ps suggests a Shockley–Read–Hall recombination mechanism. The simultaneous observation of electrons and holes with extreme ultraviolet transient absorption spectroscopy paves the way for investigating few- to sub-femtosecond dynamics of both holes and electrons in complex semiconductor materials and across junctions.

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Section: Discussionmentioning

confidence: 99%

Direct and simultaneous observation of ultrafast electron and hole dynamics in germanium

et al. 2017

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“…Attosecond transient reflectivity in the XUV and x-ray regions of the spectrum offers promise to provide the real and imaginary parts of the complex dielectric function in excitedstate materials [225]. By introducing circularly polarized light fields for pump and probe, it will be possible to investigate the topological phase in excited states or symmetry-protected spin systems.…”

Section: Advances In Science and Technology To Meet Challengesmentioning

confidence: 99%

Roadmap of ultrafast x-ray atomic and molecular physics

Young

Ueda

Gühr

et al. 2018

J. Phys. B: At. Mol. Opt. Phys.

287

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X-ray free-electron lasers (XFELs) and table-top sources of x-rays based upon high harmonic generation (HHG) have revolutionized the field of ultrafast x-ray atomic and molecular physics, largely due to an explosive growth in capabilities in the past decade. XFELs now provide unprecedented intensity (10 20 W cm −2 ) of x-rays at wavelengths down to ∼1 Ångstrom, and HHG provides unprecedented time resolution (∼50 attoseconds) and a correspondingly large coherent bandwidth at longer wavelengths. For context, timescales can be referenced to the Bohr orbital period in hydrogen atom of 150 attoseconds and the hydrogen-molecule vibrational period of 8 femtoseconds; wavelength scales can be referenced to the chemically significant carbon K-edge at a photon energy of ∼280 eV (44 Ångstroms) and the bond length in methane of ∼1 Ångstrom. With these modern x-ray sources one now has the ability to focus on individual atoms, even when embedded in a complex molecule, and view electronic and nuclear motion on their intrinsic scales (attoseconds and Ångstroms). These sources have enabled coherent diffractive imaging, where one can image non-crystalline objects in three dimensions on ultrafast timescales, potentially with atomic resolution. The unprecedented intensity available with XFELs has opened new fields of multiphoton and nonlinear x-ray physics where behavior of matter under extreme conditions can be explored. The unprecedented time resolution and pulse synchronization provided by HHG sources has kindled fundamental investigations of time delays in photoionization, charge migration in molecules, and dynamics near conical intersections that are foundational to AMO physics and chemistry. This roadmap coincides with the year when three new XFEL facilities, operating at Ångstrom wavelengths, opened for users (European XFEL, Swiss-FEL and PAL-FEL in Korea) almost doubling the present worldwide number of XFELs, and documents the remarkable progress in HHG capabilities since its discovery roughly 30 years ago, showcasing experiments in AMO physics and other applications. Here we capture the perspectives of 17 leading groups and organize the contributions into four categories: ultrafast molecular dynamics, multidimensional x-ray spectroscopies; high-intensity x-ray phenomena; attosecond x-ray science.

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Attosecond transient reflectivity of electron dynamics in germanium

Abstract: Attosecond transient reflectivity in the extreme ultraviolet is developed for monitoring band-gap excitation dynamics in germanium. The investigations unravel the fastest carrierscattering processes on the few-femtosecond time scale, and carrier thermalization on longer time scales.

Cited by 2 publications

References 7 publications

Direct and simultaneous observation of ultrafast electron and hole dynamics in germanium

Direct and simultaneous observation of ultrafast electron and hole dynamics in germanium

Roadmap of ultrafast x-ray atomic and molecular physics

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