研究目的
Investigating the dependence of the terahertz (THz) nonlinearity of graphene on the free carrier concentration and its temporal dynamics.
研究成果
The study demonstrates a wide-range control of the THz nonlinearity of graphene by gating, showing a strong dependence on the background electron population. It concludes that substantial doping is required for the THz nonlinearity of graphene.
研究不足
The time resolution of the experiment was ~2 ps due to the noncollinear pump-probe geometry employed. The study is limited to the range of doping densities examined and does not explore interband transitions.
1：Experimental Design and Method Selection:
The study employs THz-pump/THz-probe spectroscopy to investigate the THz nonlinearity of graphene. The methodology involves varying the doping concentration in graphene through gating and observing the effects on THz absorption bleaching.
2：Sample Selection and Data Sources:
A gated graphene sample designed as a field-effect transistor device is used, where the doping concentration is varied electro-chemically.
3：List of Experimental Equipment and Materials:
The setup includes a Ti:sapphire laser for generating THz pulses via optical rectification in a LiNbO3 crystal for pumping and a ZnTe crystal for probing.
4：Experimental Procedures and Operational Workflow:
The sample is pumped by strong single-cycle THz pulses and probed by weaker THz pulses to observe the pump-induced response. The doping level is varied by adjusting the gating voltage.
5：Data Analysis Methods:
The nonlinear THz field-induced carrier dynamics are described using a thermodynamic model based on the Boltzmann equation of intraband conductivity.
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