Kavli Affiliate: Alessandra Lanzara
| First 5 Authors: Maximilian Huber, Yi Lin, Giovanni Marini, Luca Moreschini, Chris Jozwiak
| Summary:
Screening, a ubiquitous phenomenon associated with the shielding of electric
fields by surrounding charges, has been widely adopted as a means to modify a
material’s properties. While so far most studies have relied on static changes
of screening through doping or gating, here we demonstrate that screening can
also drive the onset of distinct quantum states on the ultrafast timescale. By
using time and angle-resolved photoemission spectroscopy we show that intense
optical excitation can drive 1T-TiSe$_2$, a prototypical charge density wave
material, almost instantly from a gapped into a semimetallic state. By
systematically comparing changes in bandstructure over time and excitation
strength with theoretical calculations we find that the appearance of this
state is likely caused by a dramatic reduction of the screening length. In
summary, this work showcases how optical excitation enables the screening
driven design of a non-equilibrium semimetallic phase in TiSe$_2$, possibly
providing a general pathway into highly screened phases in other strongly
correlated materials.
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