| 1. |
- Hellmann, S., et al.
(author)
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Time-resolved x-ray photoelectron spectroscopy at FLASH
- 2012
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In: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 14
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Journal article (peer-reviewed)abstract
- The technique of time-resolved pump-probe x-ray photoelectron spectroscopy using the free-electron laser in Hamburg (FLASH) is described in detail. Particular foci lie on the macrobunch resolving detection scheme, the role of vacuum space-charge effects and the synchronization of pump and probe lasers. In an exemplary case study, the complete Ta 4f core-level dynamics in the layered charge-density-wave (CDW) compound 1T-TaS2 in response to impulsive optical excitation is measured on the sub-picosecond to nanosecond timescale. The observed multi-component dynamics is related to the intrinsic melting and reformation of the CDW as well as to extrinsic pump-laser-induced vacuum space-charge effects.
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| 2. |
- Hellmann, S., et al.
(author)
-
Ultrafast Melting of a Charge-Density Wave in the Mott Insulator 1T-TaS2
- 2010
-
In: Physical Review Letters. - 1079-7114. ; 105:18
-
Journal article (peer-reviewed)abstract
- Femtosecond time-resolved core-level photoemission spectroscopy with a free-electron laser is used to measure the atomic-site specific charge-order dynamics of the charge-density wave in the Mott insulator 1T-TaS2. After strong photoexcitation, a prompt loss of charge order and subsequent fast equilibration dynamics of the electron-lattice system are observed. On the time scale of electron-phonon thermalization, about 1 ps, the system is driven across a phase transition from a long-range charge ordered state to a quasiequilibrium state with domainlike short-range charge and lattice order. The experiment opens the way to study the nonequilibrium dynamics of condensed matter systems with full elemental, chemical, and atomic-site selectivity.
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| 3. |
- Horio, M., et al.
(author)
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Oxide Fermi liquid universality revealed by electron spectroscopy
- 2020
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In: Physical Review B. - 2469-9969 .- 2469-9950. ; 102:24
-
Journal article (peer-reviewed)abstract
- We present a combined soft x-ray and high-resolution vacuum-ultraviolet angle-resolved photoemission spectroscopy study of the electron-overdoped cuprate Pr1.3-xLa0.7CexCuO4 (PLCCO). Demonstration of its highly two-dimensional band structure enabled precise determination of the in-plane self-energy dominated by electron-electron scattering. Through analysis of this self-energy and the Fermi liquid cut-off energy scale, we find-in contrast to hole-doped cuprates-a momentum isotropic and comparatively weak electron correlation in PLCCO. Yet, the self-energies extracted from multiple oxide systems combine to demonstrate a logarithmic divergent relation between the quasiparticle scattering rate and mass. This constitutes a spectroscopic version of the Kadowaki-Woods relation with an important merit-the demonstration of Fermi liquid quasiparticle lifetime and mass being set by a single energy scale.
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