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arXiv · 2007.13355

Ultrafast triggering of insulator-metal transition in two-dimensional VSe$_2$

Deepnarayan 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 Lanata·Søren Ulstrup
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Abstract

Assembling transition metal dichalcogenides (TMDCs) at the two-dimensional (2D) limit is a promising approach for tailoring emerging states of matter such as superconductivity or charge density waves (CDWs). Single-layer (SL) VSe$_2$ stands out in this regard because it exhibits a strongly enhanced CDW transition with a higher transition temperature compared to the bulk in addition to an insulating phase with an anisotropic gap at the Fermi level, causing a suppression of anticipated 2D ferromagnetism in the material. Here, we investigate the interplay of electronic and lattice degrees of freedom that underpin these electronic phases in SL VSe$_2$ using ultrafast pump-probe photoemission spectroscopy. In the insulating state, we observe a light-induced closure of the energy gap on a timescale of 480 fs, which we disentangle from the ensuing hot carrier dynamics. Our work thereby reveals that the phase transition in SL VSe$_2$ is driven by electron-lattice coupling and demonstrates the potential for controlling electronic phases in 2D materials with light.

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Deepnarayan 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 Lanata, Søren Ulstrup. 2020-07-27. Ultrafast triggering of insulator-metal transition in two-dimensional VSe$_2$. https://doi.org/10.1021/acs.nanolett.0c04409

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