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(a) The total electric field transmitted through the graphene sample is plotted as a function of the (real) time t and the delay τ between the two THz pulses. (b) The total nonlinear THz signal. (c) The 2D Fourier transform of the nonlinear signal allows us to separate out the various nonlinear (third order) contributions. Only pump-probe signals are present, and no four-wave mixing (4WM). (d) Measured pump-probe signals (amplitude averaged over time) at different sample temperatures. (e) Temperature dependence of the amplitude of the pump-probe signal.
Source publication
With two-dimensional THz spectroscopy the dynamics of low-energy
carriers in graphene is determined. Both intra- and interband absorption
contribute to the observed ultrafast pump-probe signals.
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Citations
... However electric fields in the THz range often experience high coupling to electronic dipoles, leading easily to multiple interactions even with electric fields of comparatively moderate amplitude. In graphene χ (5) and higher processes lead to high harmonic generations [151,152], while in semiconductors such as InSb processes as high as χ (11) have been observed using three THz pulses [153]. Such an approach is only enabled by the collinear character of THz multidimensional spectroscopy, where the nonlinear response at multiple orders is collected in a single experiment. ...
Zur Untersuchung nichtlinearer Reaktionen von kondensierten Materie-Systemen wird die multidimensionale Terahertz-Spektroskopie genutzt. Ein mehrere Oktaven umfassende THz-Quelle, die auf der Frequenzmischung in organischen Kristallen basiert, wird entwickelt und zur Erforschung der Librationsbande von Wasser-Nanotröpfchen in DOPC-Micellen verwendet. Die nichtresonante THz-Strahlung wird genutzt, um die Emission im mittleren Infrarotbereich eines Intersubband-Übergangs von GaAs-Quantentöpfen kohärent zu steuern. Schließlich wird die 2D-THz-Spektroskopie verwendet, um die nichtlineare Antwort einer "soft-mode" in einem Aspirin-Molekül-Kristall zu studieren.
