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• Chinese Optics Letters
• Vol. 20, Issue 9, 093701 (2022)
Tingyuan Jia1、2、3, Shaoming Xie1、2, Zeyu Zhang1、2、3、4、*, Qinxue Yin1、3, Chunwei Wang1、2、3、5, Chenjing Quan1、2, Xiao Xing1, Juan Du1、2、3、4、**, and Yuxin Leng1、2、3、5、***
Author Affiliations
• 1State Key Laboratory of High Field Laser Physics and CAS Center for Excellence in Ultra-intense Laser Science, Shanghai Institute of Optics and Fine Mechanics (SIOM), Chinese Academy of Sciences (CAS), Shanghai 201800, China
• 2Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
• 3Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou 310024, China
• 4School of Physics and Electronics, Shandong Normal University, Jinan 250014, China
• 5School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
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Tingyuan Jia, Shaoming Xie, Zeyu Zhang, Qinxue Yin, Chunwei Wang, Chenjing Quan, Xiao Xing, Juan Du, Yuxin Leng. Role of the interlayer interactions in ultrafast terahertz thermal dynamics of bilayer graphene[J]. Chinese Optics Letters, 2022, 20(9): 093701 Copy Citation Text show less

Abstract

Bilayer graphene, which is highly promising for electronic and optoelectronic applications because of its strong coupling of the Dirac–Fermions, has been studied extensively for the emergent correlated phenomena with magic-angle manipulation. Due to the low energy linear type band gap dispersion relationship, graphene has drawn an amount of optoelectronic devices applications in the terahertz region. However, the strong interlayer interactions modulated electron-electron and electron-phonon coupling, and their dynamics in bilayer graphene have been rarely studied by terahertz spectroscopy. In this study, the interlayer interaction influence on the electron-electron and the electron-phonon coupling has been assigned with the interaction between the two graphene layers. In the ultrafast cooling process in bilayer graphene, the interlayer interaction could boost the electron-phonon coupling process and oppositely reduce the electron-electron coupling process, which led to the less efficient thermalization process. Furthermore, the electron-electron coupling process is shown to be related with the electron momentum scattering time, which increased vividly in bilayer graphene. Our work could provide new insights into the ultrafast dynamics in bilayer graphene, which is of crucial importance for designing multi-layer graphene-based optoelectronic devices.

1. Introduction

Bilayer graphene (BLG) is a kind of graphene composed of two coupled honeycomb-like carbon layers[1]. The strong interaction of the Dirac–Fermions in BLG has driven new insight into the strong correlation phenomena such as superconductor and correlated insulator phases in the magic-angle twisted BLG systems[26]. During the phase diagram investigating the Bardeen–Cooper–Schrieffer (BCS) state and Bose–Einstein condensate (BEC) crossover in the magic-angle graphene system, the large critical temperature (Tc) and Fermi temperature ($TF$) make the weak electron-phonon (e-p) coupling system in BCS theory not applicable to describe the emergent phenomena in the twist BLG (TBG)[2]. Therefore, it is crucial to investigate the effect of the layer-layer interaction on the electron-electron (e-e) and e-p coupling in BLG in the ultrafast time scale. Kar et al. studied the response of the photoexcited hot carriers to terahertz (THz) fields in low and moderately doped BLG deposited on a quartz substrate, which shows that the relaxation dynamics is dominated by carrier disorder interaction along with carrier acoustic phonon interactions, as compared to charge-impurity Coulomb interaction or carrier surface phonon interaction[7]. Recently, by means of high-pressure treatment, the ultrafast hot electron cooling process in BLG was interpreted as a strong interlayer shear phonon coupling, which could accelerate the relaxation dynamics[8]. However, the impact of strong interlayer coupling on the THz response, which is more sensitive to the electrons near the Fermi energy, had been seldom discussed[9].

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Tingyuan Jia, Shaoming Xie, Zeyu Zhang, Qinxue Yin, Chunwei Wang, Chenjing Quan, Xiao Xing, Juan Du, Yuxin Leng. Role of the interlayer interactions in ultrafast terahertz thermal dynamics of bilayer graphene[J]. Chinese Optics Letters, 2022, 20(9): 093701
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