Details

Autor(en) / Beteiligte

• Simoncig, Alberto
• Stupar, Matija
• Ressel, Barbara
• Saha, Tanusree
• Ribic, Primoz Rebernik
• De Ninno, Giovanni

Titel

Dissecting Mott and charge-density wave dynamics in the photoinduced phase of 1T− TaS2

Ist Teil von

• Physical review. B, 2021-04, Vol.103 (15), p.1

Ort / Verlag

College Park: American Physical Society

Erscheinungsjahr

2021

Quelle

American Physical Society Journals

Beschreibungen/Notizen

• The two-dimensional transition-metal dichalcogenide 1T− TaS2 is a complex material standing out for its puzzling low temperature phase marked by signatures amenable to both Mott-insulating and charge-density wave states. Electronic Mott states, coupled to a lattice, respond to coherent optical excitations via a modulation of the lower (valence) Hubbard band. Such dynamics is driven by strong electron-phonon coupling and typically lasts for tens of picoseconds, mimicking coherent structural distortions. Instead, the response occurring at the much faster timescale, mainly dominated by electronic many-body effects, is still a matter of intense research. By performing time- and angle-resolved photoemission spectroscopy, we investigated the photoinduced phase of 1T− TaS2 and found out that its lower Hubbard band promptly reacts to coherent optical excitations by shifting its binding energy towards a slightly larger value. This process lasts for a time comparable to the optical pump pulse length, mirroring a transient change of the onsite Coulomb repulsion energy (U). Such an observation suggests that the correction to the bare value of U, ascribed to the phonon-mediated screening which slightly opposes the Hubbard repulsion, is lost within an interval of a few tens of femtoseconds and can be understood as a fingerprint of electronic states largely decoupled from the lattice. Additionally, these results enforce the hypothesis, envisaged in the current literature, that the transient photoinduced states belong to a sort of crossover phase instead of an equilibrium metallic one.