posted on 2021-02-18, 17:13authored byDeepnarayan Biswas, Alfred J. H. Jones, Paulina Majchrzak, Byoung Ki Choi, Tsung-Han Lee, Klara Volckaert, Jiagui Feng, Igor Marković, Federico Andreatta, Chang-Jong Kang, Hyuk Jin Kim, In Hak Lee, Chris Jozwiak, Eli Rotenberg, Aaron Bostwick, Charlotte E. Sanders, Yu Zhang, Gabriel Karras, Richard T. Chapman, Adam S. Wyatt, Emma Springate, Jill A. Miwa, Philip Hofmann, Phil D. C. King, Young Jun Chang, Nicola Lanatà, Søren Ulstrup
The
transition-metal dichalcogenide VSe2 exhibits an
increased charge density wave transition temperature and an emerging
insulating phase when thinned to a single layer. Here, we investigate
the interplay of electronic and lattice degrees of freedom that underpin
these phases in single-layer VSe2 using ultrafast pump–probe
photoemission spectroscopy. In the insulating state, we observe a
light-induced closure of the energy gap, which we disentangle from
the ensuing hot carrier dynamics by fitting a model spectral function
to the time-dependent photoemission intensity. This procedure leads
to an estimated time scale of 480 fs for the closure of the gap, which
suggests that the phase transition in single-layer VSe2 is driven by electron–lattice interactions rather than by
Mott-like electronic effects. The ultrafast optical switching of these
interactions in SL VSe2 demonstrates the potential for
controlling phase transitions in 2D materials with light.