Einstein first correctly predicted how mass deflects light. Galaxy clusters, comprising of up to hundreds of galaxies all residing in a still larger dark...
Mar14
Ultrafast Electron Dynamics in Polar Liquids and Crystals
Thomas Elsaesser, Max-Born-Institute
-
Electron transfer and charge transport are most elementary processes in liquid and solid condensed matter. Both femtosecond spectroscopy and structure-resolving x-ray methods give insight in electron dynamics at atomic length and time scales. This talk focuses on many-body dynamics of free electrons in water and alcohols, and on soft-mode excitations in polar crystals.
The electric dipole moment of water molecules gives rise to a strong local electric field in the liquid which fluctuates in a time range from tens of femtoseconds to several picoseconds. The fluctuating field induces spontaneous tunneling ionization of water molecules which can be made irreversible by imposing an external directed terahertz (THz) field on the liquid [1]. Time-resolved nonlinear THz spectroscopy [2] allows for mapping charge separation, transport, and localization of the released electron on a few-picosecond time scale. The highly polarizable localized electrons modify the THz dielectric function of water, a manifestation of a highly nonlinear response. The solvated electrons exhibit pronounced polaronic properties, due to many-body Coulomb interactions with a large number of solvent molecules [3].
Soft-mode excitations of polar and/or ionic crystals display a hybrid character with coupled nuclear and electronic motions. Femtosecond x-ray powder diffraction allows for following such correlated dynamics at the atomic level by providing momentary atom positions and charge density distributions [4]. In cubic boron nitride, transverse acoustic two-phonon excitations in the electronic ground state induce a step-like increase of diffracted x-ray intensity, opposite to a Debye-Waller behavior [5]. Transient charge density maps reveal distinctly different length scales of nuclear and electronic displacements and a spatial transfer of valence charge from the interstitial region onto boron and nitrogen atoms. Such findings will be discussed in comparison to other prototypical materials.
[1] A. Ghalgoui, L.-M. Koll, B. Schütte, B. P. Fingerhut, K. Reimann, M. Woerner, T. Elsaesser, J. Phys. Chem. Lett. 11, 7717 (2020).
[2] K. Reimann, M. Woerner, T. Elsaesser, J. Chem. Phys. 154, 120901 (2021).
[3] A. Ghalgaoui, B. P. Fingerhut, K. Reimann, T. Elsaesser, M. Woerner, Phys. Rev. Lett. 126, 097401 (2021).
[4] F. Zamponi, P. Rothhardt, J. Stingl, M. Woerner, T. Elsaesser, Proc. Nat. Acad. Sci. USA 109, 5207 (2012).
[5] S. Priyadarshi, I. Gonzalez-Vallejo, C. Hauf, K. Reimann, M. Woerner, T. Elsaesser, Phys. Rev. Lett., in press.
About Thomas Elsaesser
Thomas Elsaesser is a director at the Max-Born-Institute, Berlin, Germany, and a full professor for experimental physics at Humboldt University, Berlin. He received a Dr. rer. nat. degree from the Technical University of Munich in 1986 and worked there as a research associate until 1993. He spent a postdoc period at AT&T Bell Laboratories, Holmdel, in 1990 and joined the newly established Max-Born-Institute in 1993. He is a fellow of the American Physical Society and the Optical Society of America and has received numerous scientific awards.
Ultrafast processes in condensed matter represent the main area of his research. Multidimensional infrared and terahertz spectroscopy of hydrogen bonds in liquids and biomolecules, ultrafast dynamics of low-energy excitations and nonlinear transport in solids, and photoinduced structural dynamics in crystalline materials are current topics of experimental work, supported by two ERC Advanced Grants.
Audience:
In case you're interested
Upcoming events
Abstract: The demonstration of energy gain by nuclear fusion in the laboratory and its eventual utilization as an unlimited energy source has been a...
Mar24
