Ultrasensitive Photoresponse of Graphene Quantum Dot in the Coulomb Blockade Regime to THz Radiation

Graphene quantum dots (GQDs) have recently attracted considerable attention, with appealing properties for terahertz (THz) technology. This includes the demonstration of large thermal bolometric effects in GQDs when illuminated by THz radiation. However, the interaction of THz photons with GQDs in the Coulomb blockade regime - single electron transport regime - remains unexplored. Here, we demonstrate the ultrasensitive photoresponse to THz radiation (from <0.1 to 10 THz) of a hBN-encapsulated GQD in the Coulomb blockade regime at low temperature (170 mK). We show that THz radiation of $\sim$10 pW provides a photocurrent response in the nanoampere range, resulting from a renormalization of the chemical potential of the GQD of $\sim$0.15 meV. We attribute this photoresponse to an interfacial photogating effect. Furthermore, our analysis reveals the absence of thermal effects, opening new directions in the study of coherent quantum effects at THz frequencies in GQDs

THz excited state level spacing in encapsulated graphene quantum dots

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THz absorption in Graphene Quantum Dots

International audienceWe study the optical response of multilayer graphene quantum dots at THz frequencies. We fabricate 73 nm diameter graphene quantum dots in an array of ~1mm 2 size. We demonstrate optical absorbance of these graphene quantum dots from 0.85 to 4.7 THz and study the absorption dependence with the temperature from 4K to 300 K

Variabilité multicentrique de l’estimée du volume tumoral métabolique total en TEP au FDG dans le cadre du PHRC multicentrique RTEP7

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Energy levels and THz optical properties in Graphene Quantum Dots

International audienceOwing to their energy level splitting in the meV range, large graphene quantum dots (size ~100 nm) are very attractive candidates for THz technology. Whereas their electronic properties have been widely studied by transport measurements, only very few works have been focused on their interaction with THz radiation. Here, we report a theoretical and experimental investigation of the optical properties at THz frequencies of large graphene quantum dots. Using a tight-binding modeling, we show the existence of spatially extended mixed-states that should couple efficiently to THz photons. Furthermore, we experimentally demonstrate THz optical absorption of an array of circular 75 nm-diameter graphene quantum dots at 4K and 300K

Evidence of Fermi level pinning at the Dirac point in epitaxial multilayer graphene

International audienceWe investigate the temperature-dependent conductivity of epitaxial multilayer graphene using THz time-domain spectroscopy and find evidence that the Fermi level in quasineutral graphene layers is pinned at the Dirac point by midgap states. We demonstrate that the scattering mechanisms result from the interplay between midgap states that dominate in the vicinity of the Dirac point and short-range potentials that govern at higher energies (>8 meV). Our results highlight the potential of multilayer epitaxial graphene for probing low-energy Dirac particles and also for THz optics

Sub-picosecond pulsed THz FET detector characterization in plasmonic detection regime based on autocorrelation technique

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Vacuum-field-induced THz transport gap in a carbon nanotube quantum dot

International audienceAbstract The control of light-matter interaction at the most elementary level has become an important resource for quantum technologies. Implementing such interfaces in the THz range remains an outstanding problem. Here, we couple a single electron trapped in a carbon nanotube quantum dot to a THz resonator. The resulting light-matter interaction reaches the deep strong coupling regime that induces a THz energy gap in the carbon nanotube solely by the vacuum fluctuations of the THz resonator. This is directly confirmed by transport measurements. Such a phenomenon which is the exact counterpart of inhibition of spontaneous emission in atomic physics opens the path to the readout of non-classical states of light using electrical current. This would be a particularly useful resource and perspective for THz quantum optics