Tracking Ultrafast Change of Multiterahertz Broadband Response Functions in a Photoexcited Dirac Semimetal Cd3As2 Thin Film
| Autor: | Natsuki Kanda, Yuta Murotani, Takuya Matsuda, Manik Goyal, Salva Salmani-Rezaie, Jun Yoshinobu, Susanne Stemmer, Ryusuke Matsunaga |
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| Rok vydání: | 2022 |
| Předmět: | |
| Zdroj: | Nano Letters. 22:2358-2364 |
| ISSN: | 1530-6992 1530-6984 |
| Popis: | The electromagnetic response of Dirac semimetals in the infrared and terahertz frequency ranges is attracting growing interest for potential applications in optoelectronics and nonlinear optics. The interplay between the free-carrier response and interband transitions in the gapless, linear dispersion relation plays a key role in enabling novel functionalities. Here we investigate ultrafast dynamics in thin films of a photoexcited Dirac semimetal Cd$_3$As$_2$ by probing the broadband response functions as complex quantities in the multiterahertz region (10-45 THz, 40-180 meV, or 7-30 $\mu$m), which covers the crossover between the inter and intraband response. We resolve dynamics of the photoexcited nonthermal electrons which merge with originally existing carriers to form a single thermalized electron gas and how it is facilitated by high-density excitation. We also demonstrate that a large reduction of the refractive index by 80% dominates the nonequilibrium infrared response, which can be utilized for designing ultrafast switches in active optoelectronics. Comment: 20 pages |
| Databáze: | OpenAIRE |
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