Tuning ultrafast electron thermalization pathways in a van der Waals heterostructure
Author(s)Massicotte, Mathieu; Watanabe, Kenji; Taniguchi, Takashi; Kong, Jing; Jarillo-Herrero, Pablo; Ma, Qiong; Andersen, Trond Ikdahl; Nair, Nityan L.; Gabor, Nathaniel M.; Lui, Chun Hung; Young, Andrea; Fang, Wenjing; Gedik, Nuh; Koppens, Frank Henricus Louis; ... Show more Show less
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Ultrafast electron thermalization—the process leading to carrier multiplication via impact ionization and hot-carrier luminescence —occurs when optically excited electrons in a material undergo rapid electron–electron scattering to redistribute excess energy and reach electronic thermal equilibrium. Owing to extremely short time and length scales, the measurement and manipulation of electron thermalization in nanoscale devices remains challenging even with the most advanced ultrafast laser techniques. Here, we overcome this challenge by leveraging the atomic thinness of two-dimensional van der Waals (vdW) materials to introduce a highly tunable electron transfer pathway that directly competes with electron thermalization. We realize this scheme in a graphene–boron nitride–graphene (G–BN–G) vdW heterostructure through which optically excited carriers are transported from one graphene layer to the other. By applying an interlayer bias voltage or varying the excitation photon energy, interlayer carrier transport can be controlled to occur faster or slower than the intralayer scattering events, thus effectively tuning the electron thermalization pathways in graphene. Our findings, which demonstrate a means to probe and directly modulate electron energy transport in nanoscale materials, represent a step towards designing and implementing optoelectronic and energy-harvesting devices with tailored microscopic properties.
DepartmentMassachusetts Institute of Technology. Department of Electrical Engineering and Computer Science; Massachusetts Institute of Technology. Department of Physics
Nature Publishing Group
Ma, Qiong; Andersen, Trond I.; Nair, Nityan L.; Gabor, Nathaniel M.; Massicotte, Mathieu; Lui, Chun Hung; Young, Andrea F. et al. “Tuning Ultrafast Electron Thermalization Pathways in a van Der Waals Heterostructure.” Nature Physics 12, no. 5 (January 18, 2016): 455–459. © 2016 Macmillan Publishers Limited, part of Springer Nature
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