Ultrafast Carrier Dynamics and Bandgap Renormalization in Layered PtSe2

• Published in: Small (Weinheim an der Bergstrasse, Germany) Vol. 15; no. 34
• Main Authors: Wang, Gaozhong, Wang, Kangpeng, McEvoy, Niall, Bai, Zhengyuan, Cullen, Conor P., Murphy, Conor N., McManus, John B., Magan, John J., Smith, Christopher M., Duesberg, Georg S., Kaminer, Ido, Wang, Jun, Blau, Werner J.
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01-08-2019
• Subjects: 2D platinum diselenide; bandgap renormalization; carrier dynamics; Chemical potential; Condensed matter physics; Energy gap; Nanotechnology; noble metal dichalcogenides; Optical measurement; Optoelectronics; Organic chemistry; Photonics; Platinum; saturable absorption; Two dimensional bodies; Two dimensional materials; Ultrafast lasers
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.201902728

Carrier interactions in 2D nanostructures are of central importance not only in condensed‐matter physics but also for a wide range of optoelectronic and photonic applications. Here, new insights into the behavior of photoinduced carriers in layered platinum diselenide (PtSe2) through ultrafast time‐resolved pump–probe and nonlinear optical measurements are presented. The measurements reveal the temporal evolution of carrier relaxation, chemical potential and bandgap renormalization in PtSe2. These results imply that few‐layer PtSe2 has a semiconductor‐like carrier relaxation instead of a metal‐like one. The relaxation follows a triple‐exponential decay process and exhibits thickness‐dependent relaxation times. This occurs along with a band‐filling effect, which can be controlled based on the number of layers and may be applied in saturable absorption for generating ultrafast laser pulses. The findings may provide means to study many‐body physics in 2D materials as well as potentially leading to applications in the field of optoelectronics and ultrafast photonics.
Transition of transient carrier dynamics from semimetal to semiconductor is observed in 2D platinum diselenide (PtSe2) films by ultrafast spectroscopy. Thickness‐dependent bandgap renormalization, transient absorption as well as carrier‐relaxation lifetimes are determined. An ultrafast (a few picoseconds) and strong (larger than MoSe2 and WS2) saturable absorption response makes PtSe2 a promising material for mid‐infrared optical devices.