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Ultrafast modulation of x-ray absorption by coherent phonon excitations



Eric L. Shirley, Jannick Weisshaupt, Michael Woerner, Marc J. Vrakking, Thomas Elsaesser, Andreas Borgschulte


X-ray absorption in solids promotes an electron from an atomic core level to the conduction band states, and near-edge spectra structure gives insight into local atomic geometry and chemical bonding effects. Based on a novel implementation of femtosecond x-ray absorption spectroscopy with a laser-driven high-harmonic source, we demonstrate the ultrafast modulation of x-ray absorption by the femtometer-scale coherent vibrational displacements. In LiBH4, displacements along an Ag phonon mode at 10 THz are induced by impulsive femtosecond Raman excitation and observed by changes in the x-ray absorption spectrum in the time domain. The Raman process involves a field-driven transfer of electronic charge from the BH4 units to neighboring Li+ ions. Our results reveal the subtle interplay of nuclear motions and electronic structure, a scenario relevant for a wide range of materials.
Physical Review B


coherent phonon, impulsive Raman, LiBH4, lithium borohydride, Raman, Raman tensor, x ray, x-ray absorption


Shirley, E. , Weisshaupt, J. , Woerner, M. , Vrakking, M. , Elsaesser, T. and Borgschulte, A. (2017), Ultrafast modulation of x-ray absorption by coherent phonon excitations, Physical Review B, [online], (Accessed June 21, 2024)


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Created February 1, 2017, Updated January 27, 2020