Dissecting Mott and charge-density wave dynamics in the photoinduced phase of 1T-TaS[sub]2
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.
2021
2021-04-13 10:10:48
1033
ultrafast phenomena, time resolved photoemission, strongly correlated systems, transition metal dichalcogenide
Alberto
Simoncig
70
Matija
Stupar
70
Barbara
Ressel
70
Tanusree
Saha
70
Primož
Rebernik Ribič
70
Giovanni
De Ninno
70
COBISS_ID
3
59328771
UDK
4
53
ISSN pri članku
9
2469-9950
DOI
15
10.1103/PhysRevB.103.155120
NUK URN
18
URN:SI:UNG:REP:OCCSHWAX
Simoncig_PhysRevB.103.155120.pdf
1401080
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