Berlin 2015 – scientific programme

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O: Fachverband Oberflächenphysik

O 69: Ultrafast Electron and Spin Dynamics

O 69.5: Poster

Wednesday, March 18, 2015, 18:15–21:00, Poster A

Coherent and incoherent electronic excitations in the Mott insulator 1T-TaS₂ — •Manuel Ligges¹, Isabella Avigo¹, Simon Freutel¹, Matthias Kalläne², Ping Zhou¹, Lutz Kipp², Kai Rossnagel², and Uwe Bovensiepen¹ — ¹Fakultät für Physik und Zentrum für Nanointegration, Universität Duisburg-Essen — ²Institut für Experimentelle und Angewandte Physik, Universität Kiel

Using femtosecond time- and angle-resolved photoemission spectroscopy we study the partial quench of charge order in the prototypical Mott insulator 1T-TaS₂ after optical excitation. An unoccupied electronic state is observed in the correlated (spectrally gapped) commensurate and nearly-commensurate charge density wave (CDW) phases of the material that is found to be abscent in the (almost metallic) incommensurate CDW phase and, thus, appears to be a direct measure of short range correlations. From its energetic position (E-E_F=170 meV), this state might be identified as the upper Hubbard band. The population of this coherent feature follows the temporal laser pulse profile and differs significantly from the incoherent electronic population dynamics in the same energetic window and k-region (Γ) that shows clear life time effects (τ≈ 150 fs). We conclude that this state directly reflects the presence of charge order in the system which promptly collapses in the presence of the laser field, leaving the system behind in a state similar to the high-temperature metallic phase.