Ultrafast filling of an electronic pseudogap in photoexcited (LaS) 1.196 VS 2

Abstract : We investigate by angle and time resolved photoemission spectroscopy the unusual insulating state of strongly distorted triangular V slabs in (LaS)1.196VS2. We show that the electronic structure is dominated by the lowest band of the V t2g manifold, which disperses over 0.7 eV and is nearly filled. Hence, (LaS)1.196VS2 is not a Mott insulator. The spectra are strongly temperature dependent, shifting by 100 meV upon cooling to 50 K. The sudden photoexcitation at 50K induces a partial filling of the electronic pseudogap within less than 80 fs. The electronic energy flows into the lattice modes on a comparable timescale. We conclude that a very strong electron-phonon coupling makes this state extremely sensitive to small perturbations of the V clusters distortions.
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Submitted on : Tuesday, June 2, 2015 - 3:00:38 PM
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V Brouet, J Mauchain, E Papalazarou, Jérôme Faure, M Marsi, et al.. Ultrafast filling of an electronic pseudogap in photoexcited (LaS) 1.196 VS 2. 2015. ⟨hal-01159053⟩

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